Added a Scala preference for Mark Occurrences

Added a toolbar button for quick access.
Fixes #1001466
The keyword 'requires' is no longer shown as keyword

The parsing is done by Scalariform. Because it treats 'requires' still as a keyword,
it needs to be translated to default content type.

Fix #1000750
Reformatting of ScalariformToSyntaxClass
Fixes problems in preference state sharing

Using only Boolean, and correctly starting the toggle handler listener.
Merge pull request #305 from sschaef/issue/requires-keyword

Issue/requires keyword
Disabled flaky debugger ``RemoteConnectorTest`` tests class

Re #1001464
Merge pull request #311 from dotta/issue/disable-debugger-remote-tests-1001464

Disabled flaky debugger ``RemoteConnectorTest`` tests class
Merge pull request #299 from skyluc/issue/mark-occurrence-preference-1001466

Added a Scala preference for Mark Occurrences