Replace IndexFile and IndexFileForProcess with IndexLocation
The new method call takes a flags parameter, allowing more control over its behaviour in Tracker 3.
The equivalent of the IndexFileForProcess method is now to call
IndexLocation(uri, ['watch-for-caller']). As before, this
enables two things: the location is watched for changes while
the calling process is connected to the bus, and the location
is un-indexed if the calling process disconnected from the bus.
This MR depends on !235 (merged)