Improved the Coq editor's automatic indentation behaviour

This is much better than it was, but -- because CoqSentence doesn't yet
support seeking backwards -- there are some occasional performance problems
Improved the performance of the Coq editor's autoindentation code

The autoindentation code now uses a simple heuristic to scan backwards for
things that look a bit like sentences. This is much, much faster than
scanning forwards through the file up to the cursor
Use a TableViewer instead of a Table in the rich goal presenter

This makes it possible to highlight bits of hypotheses, which this commit
also implements. (This actually introduces a little transitional bug:
highlighting bits of the the goal no longer works! This will be fixed very
soon.)
Create both SashGoalPresenter controls at the same time

This allows the controls to refer to each other cleanly, which in turn
makes the goal identifier highlighting work properly again
Bumped the version numbers to 0.4.4 and added a changelog entry

This commit also adds dates to all the previous changelog entries