Refactoring quick fix adjustments to caret and selection handling

Refactoring quick fix adjustments to caret and selection handling

This changeset changes the logic in the refactoring quickfix (which
adds the Android refactorings based on the current caret position,
lexical context and selection).

It now allows some of the refactorings to be run when there is a
selection (this fixes "20393: Extract string functionality in Android
XML files"), and it makes other refactorings work when there is no
selection (it implicitly selects the surrounding element).

It also ensures that the Extract Style refactoring won't be listed at
the top if the attribute under the cursor is not a stylable attribute,
and it makes some other adjustments to the proposal order.
Change-Id: I0714bb652032aa19e6c2502dc1af7bb5e4adf308