LatinIME: Add shortcuts support

Making sure to include unit test changes this time.
Adjust for deleted files and delete references to them.

This reverts commit fe674a44,
"am 12d80ebe: Remove shortcut support from LatinIME."

Ticket-Id: CYNGNOS-3129, CYNGNOS-3267
Change-Id: I136e307f93445b353e0d798284fd0fbaee61c0d9