Inserts of directories can be done in bulk as long as they're inserted before
the files contained within. Extend MediaInserter to accommodate giving priority
treatment to directories.
Bulk deleting of entries can be further sped up (by a factor of ~3 in my tests)
by deleting entries in database order. Switch the file cache to use
LinkedHashMap instead of HashMap to allow iterating over the cache in database
order. Also use bindArgs to allow for better caching of sql statements.
Change-Id: Ieb9ffc4e866c6cd505bf795eb80ff5d03ffc56bd
d121cfcbb4