add help menu item to open prefs file
JSLint
create empty settings file if it doesn’t exist
Merge branch 'PreferencesModel' into couzteau/open_prefs_file
 review feedback
move command to debug menu and change wording to “Open Preferences File”
Adjust a few minor things from code review.
Merge branch 'adobe-couzteau/open_prefs_file' into PreferencesModel

Conflicts:
	src/preferences/PreferencesManager.js