libtracker-miner: IndexingTree _new() now takes a GFile

If NULL is passed, then it defaults to the behaviour before, which is to use
file:/// as the root node.
libtracker-miner: Fix typo, "suffix" is really "prefix"
libtracker-miner: FileSystem _new() now takes GFile for root

If NULL is passed, then it defaults to the behaviour before, which is to use
file:/// as the root node
libtracker-miner: Allow FileNotifier to have external crawlers
libtracker-miner: Make it possible to use external crawlers for data mining
tracker-miner-fs: Make sure we work with the new changes to MinerFS
libtracker-miner: Added MinerFSError quark for GErrors returned
libtracker-miner: Miner now uses a proper MinerError API

Previously, the error code was always 0. Now we have an enum people can refer
to.

This is particularly important for miner implementations and cases where
classes want to return an error due to an API being used *while* being paused.
This is the case in TrackerMinerFS.
libtracker-miner: Introduce MinerFSQueue for injecting file changes

This is used to signal TrackerFileNotifier and TrackerMinerFS from external
crawlers about files and what has happened regarding them.
libtracker-common: Enable G_MESSAGES_DEBUG for verbosity > 1, not 2

g_info() or G_LOG_LEVEL_INFO requires this to see output.
libtracker-miner: Fix warning on root GFile unref in FileSystem
libtracker-miner: Add log information about locations started in FileNotifier
libtracker-miner: Fix paused check in MinerFS before notifying files
libtracker-miner: Document and group functions for MinerFS in header
libtracker-miner: Removed MinerFS _manually_notify_file() and Queue enum
libtracker-miner: Added TrackerEnumerator interface, TrackerFileEnumerator class

These are used to enumerate over children of a URI. The TrackerFileEnumerator
uses GFileEnumerator and the TrackerEnumerator allows for other
implementations to supply GFile/GFileInfo data to Tracker for 3rd parties.

Updated MinerFS TrackerDirectory flags for external crawlers
libtracker-miner: Added FileEnumerator unit test
libtracker-miner: Don't iterate the wrong enumerator, avoids warnings on no dir
libtracker-miner: Don't create Crawler until FileNotifier is constructed

We don't have the Enumerator until constructed.
libtracker-miner: Make sure we free enumerator data on success in Crawler