Docs (mostly): enumerate JELLY_BEAN target SDK changes.

Okay this isn't entirely docs.  I have un-hidden the new permission
for binding to accessibility services; we were going to go out with
it hidden since it didn't go into factory ROM, but now that we are
doing other things we might as well expose it.

Also changed a log from E to W, since it is not an error.

Change-Id: I9226c95e3b63e12218fe41dc3f4290d9824a9e5c