Remove preference store listener on deactivation

The listener would try to redraw a disposed widget on preference changes, even after
the editor was closed.
Merge pull request #661 from dragos/master

Remove preference store listener on deactivation
Merge pull request #662 from huitseeker/issue/morelints

Cleans up more warts (mostly Option-related)
remove some deprecations
Upgrades savePluginPreferences
Extends coverage of CompilerSettingsTest
Replaces PropertyStore with sparser platform calls.

PropertyStore.setValue overridden for compatibility with <= Juno.