Merged latest lindenlab/viewer-development with mani_linden/viewer-development for bacground updater work.

Modified code in indicated changeset to correct problem after consulting with
 Leyla Linden who sugested the orginal change. This fix will convert the Legacy
 name to a user name id not useing Display Names.

Reviewed by mani.

Added opaque water default settings to Linux featuretable.

STORM-576 FIXED Hooked up code to preference that allows users to enable double-click to teleport or use auto-pilot.

- Added dirty flag that is set true when user changes checkbox or chooses one of radiobuttons connected to double-click action. No change of user settings happens on this commit, because user may press cancel or close floater. If user presses OK, and flag is true, user changes are applied to settings.
If user clicks cancel or closes floater, controls are reverted to the state they were before changes, using settings to determine it.

- Removed double-click action menu items and code that handled them to avoid functionality duplication and synchronization problems.

Toggling the setting now calls LLUpdaterService::startChecking() and LLUpdaterService::stopChecking(), which enable and disable the service.