Add dynamic Preferences indexing (part 2)

- change the Index SQL model. Add a new "enabled" column.
- use that column for issuing a more restrictive search query
- change the SearchIndexProvider API to pass the "enable" state
- apply it to Bluetooth settings
- refactor the list of indexable resources (SearchIndexableResources)

Change-Id: Ic900fb27cb12a285a80d953aa1aa88f0070cd986
9 files changed