Added content-type w/ charset to stop getting error from FF in error log.
IDEA inspection changes
Added CreatePreferenceMap() and UpdatePreferences() functions, built out update map (mostly commented out atm), built new preference map object.

Snaplinks is still using the old preferences object and mappings, only mapping change thus far is Dev* stuff.  Changing the preference system to be more
fluent, such as Prefs.Activation.RequiresShift which is represented in prefs branch as extensions.snaplinks.Activation.RequiresShift.
REFACTOR: Refactored all Preference items to utilize new SLPrefs, eliminated SnapLinksPrefClass.
REFACTOR: Numerous old-school identifiers in options
REMOVED: No longer used Utility.js:PrefsMapper class