This allows developers to force a particular module is used over all
the others available.

when called on the command line, sparql builders length wasn't being
checked.

In case of error, NULL TrackerSparqlBuilders will be returned by
get_file_metadata().

A somewhat more descriptive name.

Now implementations must open/close inserts themselves, since more
than just inserts could be added there.

The first argument will be preinserts, which are the necessary
insertions that actual file metadata rely on. The second argument
is just a collection of data triples so it can be inserted together
with the rest of the data in the miner.

Was in tracker-extract/tracker-main.h

If verbosity is > 0 for tracker-store, the log will show:

<--- [%d|%s] Hello World

Where %d is the request ID and %s is the basename of the command that
sent the D-Bus request in. For example "tracker-stats".

This removes the following line:
/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*- */

This is not needed and editors should work without this anyway.

When INTO or FROM are passed, graph in tracker_writeback_check wont be NULL.
A NULL graph means 'default graph' or 'something that came from the user'.
We only want to do writeback for things that came from the user. This is how
we distinguish between content from the miner and content from the user.

This allows us to use verbosity=1 to just see the SPARQL output and
nothing else.

Now we do the processing in tracker-extract and only request the
thumbnail for the albumart to be queued from tracker-miner-fs. This
saves us sending potentially large album art over dbus

Now we signal data that is used to be processed for albumart. This is
all handled in the miner-fs now, so the extractors simply say, here is
my data and length of data (and some other details like artist), now
process it. The miner-fs then uses the code previously
tracker-extract-albumart.c to either download the art, use GdkPixbuf
or save the data directly to the right filename. The thumbnails are
then requested staight after.

Also added an initial dbus signal for tracker-extract to be able to
tell the tracker-miner-fs about new files that need thumbnailing.