Flatten data properties

[jouni]

The current nested properties syntax for some of the API is not very Polymer-like, and seems more complex than needed.

Proposal:

data.source (array) -> items
data.source (function) -> datasource
data.sortOrder -> sortOrder (notify: true)
data.clearCache() -> clearCache()
data.getItem() -> getItem()

Keep the old API available, but output a deprecation warning to the browser console that the old API will be removed in the next minor version.

Collateral damage (needs to be done also):

• Update code examples
  • Polymer integration example should be refactored to showcase the Polymer “databindability”
• Update API docs
• Update tests
• Write clear release notes / migration guide about the changes
• Update JSFiddles
• READMEs
• Notify marketing to update demos

[jouni]

We could still keep the current API working at the same time, but deprecate it.