Rebuild Scala projects after a global compiler settings change.

If the user changes compiler settings on the Scala Preferences page, all Scala
projects that 'inherit' these settings should be rebuild. The existing logic
was dealing only with the case where *project-specific* settings were changed.

Fixed #1001460.
Merge pull request #290 from dragos/issue/settings-refresh-build-1001460

Rebuild Scala projects after a global compiler settings change.