Added constructor overloads for TelemetryConfiguration and added creation of a default InMemoryChannel when no channel is specified for a new instance. TelemetryClient will no longer create an InMemoryChannel on the configuration instance if TelemetryChannel is null, instead the configuration instances will always have a channel when created.
TelemetryConfiguration will no longer dispose of user provided ITelemetryChannel instances. Users must properly dispose of any channel instances which they create, the configuration will only auto-dispose of default channel instances it creates when none are specified by the user.

All issues from this list:
https://github.com/Microsoft/ApplicationInsights-dotnet/milestone/13?closed=1

• Added metric aggregation functionality via MetricManager and Metric classes.
• Exposed a source field on RequestTelemetry. This can be used to store a representation of the component that issued the incoming http request.

• Includes all changes since 2.1.0 stable release.

• Added serialization of the "source" property.
• Downgraded package dependencies to Microsoft.NETCore.App 1.0.1 level.
• Fixed the priority of getting an iKey from an environment variable
• Moved from PCL dotnet5.4 to .NET Core NetStandard1.5.
• Updated dependency versions.

• Payload sanitization for RichPayloadEventSource.
• Fix to fallback to an environment variable for instrumentation key when not specified when initializing TelemetryConfiguration.
• RoleInstance and NodeName are initialized with the machine name by default.
• Read InstrumentationKey from environment variable APPINSIGHTS_INSTRUMENTATIONKEY if it is was not provided inline. If provided it overrides what is set though configuration file. (Feature is not available in PCL version of SDK).
• Context properties NetworkType, ScreenResolution and Language marked as obsolete. Please use custom properties to report network type, screen resolution and language. Values stored in these properties will be send as custom properties.
• Dependency type was updated to reflect the latest developments in Applicaiton Insights Applicaiton Map feature. You can set a new field - Target. CommandName was renamed to Data for consistancy with the Application Analytics schema. DependencyKind will never be send any more and will not be set to "Other" by default. Also there are two more constructors for DependencyTelemetry item.
• Type SessionStateTelemetry was marked obsolete. Use IsFirst flag in SessionContext to indicate that the session is just started.
• Type PerformanceCounterTelemetry was marked obsolete. Use MetricTelemetry instead.
• Marked RequestTelemetry.HttpMethod as obsolete. Put http verb as part of the name for the better grouping by name and use custom properties to report http verb as a dimension.
• Marked RequestTelemetry.StartTime as obsolete. Use TimeStamp instead.
• Removed BCL dependency
• Added IPv6 support
• Fixed an issue where channels sent expired data from storage
• Fixed an issue where the clock implementation would accumulate error
• Fixed an issue where telemetry with emptry properties would be dropped
• Added support for SDK-side throttling

• InMemoryChannel has a new override for Flush method that accepts timeout.
• Local storage folder name was changed. That means that when the application stopped, and the application was updated to the new SDK, then the telemetry from the old local folder will not be send.
• Allow all characters in property names and measurements names.
• AdaptiveTelemetryProcessor has a new property IncludedTypes. It gets or sets a semicolon separated list of telemetry types that should be sampled. If left empty all types are included implicitly. Types are not included if they are set in ExcludedTypes.
• Richpayload event source event is generated for all framework versions of SDK (before it was supported in 4.6 only)
• TelemetryClient has a new method TrackAvailability. Data posted using this method would be available in AppAnalitics only, Azure portal UI is not available at this moment.

• Add ExceptionTelemetry.Message property. If it is provided it is used instead of Exception.Message property for the outer-most exception.
• Telemetry types can be excluded from sampling by specifying the ExcludedTypes property (Add ExcludedTypes element under AdaptiveSampling telemetry processor node with ';'-separated list. Possible types are "Dependency", "Event", "Exception", "PageView", "Request", "Trace").
• ServerTelemetryChannel: changed backoff logic to be less aggressive, added diagnostics event when backoff logic kicks in and added more tracing. (Done to address issues when data stops flowing until an application gets restarted)

No code changes since beta4.

• Bug fix

• Support partial success (206) from the Application Insights backend. Before this change SDK may have lost data because some items of the batch were accepted and some items of the batch were asked to be retried (because of burst throttling or intermittent issues).
• Bug fixes