Remove the subtypes that don't get a dictionary any more in AOSP.
Also prepare for all downloadable-dictionary supported subtypes.
Bug: 7673670
Change-Id: I5b754a791233c270237b8f7e5e2208f7282ad294
Note that this is not enough: we still need to create a
reasonable proximity table for Cyrillic characters, or we
won't be able to show up suggestions.
Bug: 5701241
Change-Id: Idb141f7a230a6e1a46094308c26f43c01ab3b97a