[performance] Speed up reading from USB

This patch allows the BulkReaderThread and the MTP responder to work
at the same time, instead of taking turns blocking.

It gives about a 20% speed improvement on Jolla hardware.
Merge pull request #45 from xhaakon/update

Enable StorageFactory tests

This PR cleans up and enables a unittest suite that had fallen out of use.
It's installed as "storagefactory-test", not to be confused with the
fsstorageplugin unit tests which are installed as "storage-test".
made some changes suggested in review
get rid of some unnecessary preprocessor usage

We are modern programmers with modern tools
Merge pull request #43 from amtep/update

[performance] Speed up reading from USB
[mtp] ignore storage ID sent in MTP object info

Some initiators leave this field zero. We should always take into
account only the storage ID parameter of MTP request. Not doing so
resulted in files ending up on the first storage (since ID 0 means
responder should choose), and if parent object was also specified, error
response with InvalidParentObject was generated.