Show "To:<Names>" in sent and outbox index views

b/13304929

The solution being delivered introduces a new folder capability:
UIProvider.FolderCapabilities.SHOW_RECIPIENTS which indicates a folder
should display "To: " in front of its participants list because it
is a folder containing outgoing mail or sent mail (thus viewing
recipients is more useful than senders). This capability is returned
for Drafts, Sent, and Outbox.

Note that extra work was required to make this function properly in
the widget we export to the launcher. See BaseWidgetProvider and
friends for details.

Change-Id: I2fa2394224ef3911992ab8d5cb67b05fdf5f3e85
12 files changed