Disable useless and expensive Java goodies for Scala sources.

* quick fixes and quick assists in Scala sources have no meaning, but may trigger pauses in the UI of more than 10 seconds
* Run As/Debug As testers may trigger hierarchy calculations, inducing 10s of seconds of delay in the UI thread, for instance when scrolling through a contextual menu. This disables 'Run As Java'

Fixed #1001434. Fixed #1001178.
Merge pull request #278 from dragos/issue/disable-quick-java-assists-1001434

Disable useless and expensive Java goodies for Scala sources.
Correct partitioning of octal sequences in character literals

The previous behavior was not correct because an octal sequence can
start not only with a '0' but with all signs between '0' and '7'.

Fix #1001443