Address Issue 1761: Grid status from Help menu

Adds Grid Status... item to Help menu

Translators:
add WebLaunchGridStatus notification translation to notifications.xml
add Grid Status... menu item translation to menu_viewer.xml and menu_login.xml

Adds menu visibility function "VisibleSecondLife" for hiding things that shouldn't be shown on OpenSim
Hides SL issue tracker and wiki menu items on non-SL grids