Correctly determine if compiler settings were changed through the UI.

Also, make sure the dialog prompt to clean all projects appears only when settings were really changed.

Fix #1002075
Remove all traces of `Trim`

This class never really pulled its wait. Since it was the root cause of
the bug just fixed, the only remaining use was removed. It conflated `String.trim` and `isEmpty`
in one go.
Merge pull request #665 from dragos/issue/rebuild-too-often

Don't clean workspace unless compiler settings really changed