Add TrackerStorage and fix license file

Added tracker-storage.[ch] from tracker-miner, and added building of marshal.[ch] (I didn't name them 'tracker-marshal.[ch]' because libmediaart might need them too afterwards aside from just tracker-storage.[ch]). I didn't test it though. I also made additional changes to fix distcheck for things I forgot last time.

For the license, currently autogen adds a COPYING file with GPLv3 license. After checking the source files, seems like they are all under LGPLv2.1, so I went to GNU's website and followed this:

'''
You should also include a copy of the license itself somewhere in the distribution of your program. All programs, whether they are released under the GPL or LGPL, should include the text version of the GPL. In GNU programs the license is usually in a file called COPYING.

If you are releasing your program under the LGPL, you should also include the text version of the LGPL, usually in a file called COPYING.LESSER. Please note that, since the LGPL is a set of additional permissions on top of the GPL, it's important to include both licenses so users have all the materials they need to understand their rights.
'''

(from https://www.gnu.org/licenses/gpl-howto.html)

I downloaded the text versions of GPLv2 and LGPLv2.1 from GNU's website then named them COPYING and COPYING.LESSER, respectively.