Remove last calls to `JavaUI.getDocumentProvider`

With the introduction of `ScalaDocumentProvider`, this method no longer
returns the correct document provider.
Merge pull request #835 from sschaef/fix-last-document-provider-calls

Remove last calls to `JavaUI.getDocumentProvider`
Don’t crash when the region is outside the underlying string.

This re-instates behaviour from before the API work.

Fixed #1002302
Merge pull request #837 from dragos/issue/semantic-highlighting-crash

Don’t crash when the region is outside the underlying string.
Make project close and plugin shutdown save (scala) project-specific preference stores as well.

Fixes #1002304, #1002243
Merge pull request #838 from huitseeker/issue/1002304

Project close & plugin shutdown save project-specific preference stores
Add link to starter tickets.
Upgrade AspectJ compiler to make it work with JDK8.
Make structure builder tests order-independent.
Don’t catch `AssertionError` in `getOption`

This caused some tests to fail under the radar, since JUnit asserts were silently logged
and not rethrown. This brings the test suite back to normal and fixes the tests that
were actually failing.
Turn off auto-building, hopefully this makes the test less flaky.
Restore correct selection when region changed at end of selection

Fixes #1002314
Merge pull request #843 from dragos/issue/missed-tests

Don’t catch `AssertionError` in `getOption`
Merge pull request #844 from sschaef/selection-lost

Restore correct selection when region changed at end of selection
Show @return in scaladoc hovers

Fixes #1002312
Merge pull request #841 from mlangc/master

Show @return in scaladoc hovers
Improve test suite
Revert "Interrupt Scala builder on resource change"
Create a build marker when a project is not built due to upstream errors.

Fixed #1002320
Merge pull request #845 from scala-ide/revert-767-t1002229-interrupt-build

Revert "Interrupt Scala builder on resource change"