Fix #34

All unit tests used to start the notifier, while it's only needed for a
single set of tests

We never run the parser from unit tests

In order not to confuse them with media we failed to parse

This will make it easier to postpone some of those operations

Playcount isn't a buffered change

This denotes that this file would know about other files (actually, the
lack of any other file), which isn't planned, expected, and would
require us to change the file type in case we add another MRL to a media

This way we can have a file which type is anything AND it's an external
file

This reduces the amount of assumptions we make based on extension.
If we fail to extract some tracks, we will start a playback as we would
for the thumbnailing process. If no video tracks are detected but no
error occur, assume it's an audio file.

Fix #4

So we avoid getting bitten by ODR

Since the public interface doesn't expose a save() method, those changes
would never be changed