Support for Call Hierarchy

[gorkem]

Add support for call hierarchies

[kittaakos]

I am volunteering for this.

The LSP part has been proposed via microsoft/vscode-languageserver-node#420.
I will also take care of the LSP4J implementation.

If this task is not yet taken, please assign to me. Thank you!

[fbricon]

@kittaakos sounds great! Seems I can't assign it to you, but feel free to start working on it

[kittaakos]

@fbricon, the org.eclipse.jdt.internal.corext.callhierarchy.CallHierarchy class is in jdt.ui. Would it be sufficient to copy the UI classes into JDT LS for now and do the jdt.core.manipulation migration in a separate PR. Thank you!

[kittaakos]

Would it be sufficient to copy the UI classes into JDT LS for now

I've created a PR for this task. After copying the JDT UI code to the LS, I had to adjust the source in two relatively easy steps: c7ea1da, 33b0a71. (The rest is the actual implementation.) I would like to know how to proceed with the org.eclipse.jdt.internal.corext.callhierarchy package.

[fbricon]

@jjohnstn @rgrunber how long before we could get those copied classes refactored to jdt.core?

[jjohnstn]

It should be straightforward. Let me work on a patch.