Structure UI Changes

Gabriel Harrison wrote:

It would be nice to have a) structure parsing for all non-project
.java files. This is not difficult but is designed to... make life
difficult for us? Not quite sure why it's disabled. b) it would be
nice if methods in this class that are overridden are bolded as they
are in the method completion tab. The Structure pane can be more
difficult to read than is necessary for large extended classes.

This would be partly difficult because I believe currently no AST is
built for non-project things, I think because many references would not
resolve because the classpath is likely not correct for that file.