For the Android Share feature, do not show Always option.

* Users are likely to use multiple apps for sharing things.
* This change prevents accidental selection of only one sharing app for eternity.
* See http://developer.android.com/guide/components/intents-filters.html#ForceChooser for guidance.
* This change also changes the lead in text for the shared link and labels the chooser as 'Share via'.
* Also, added some qqq hints above and beyond share-related stuff.

Change-Id: I86cef2517ac75878a89caff678aa70835dbee121