Switched to using json for preferences.  No custom vs. default yet
Implemented custom and user json entries
Taking default preferences from prefs.json
Setup temporary prefs json file and classes
Setup prefs for key bindings, fonts, and theme.  Pulled out getter / setters
Migrate old values to JSON prefs
Merge branch 'master' of https://github.com/dart-lang/chromedeveditor into umop-preferences_phase1
Cleaned up, removed commented code, and added line to end of prefs.json
changed to use width and useTabs
Review fixes
Review fixes: Removing migration code
resolved conflicts
Merge pull request #3257 from dart-lang/umop-preferences_phase1

JSON preferences (still using prefs panel)