Please describe the problem:
The DAAP song list is currently missing the year even if the ID3 year tag is
encoded in the file.  This is because the year information is not currently
being extracted into the rhythmbox data structure.

This patch implements the year extraction for files taken from a DAAP stream.

Steps to reproduce:
1. rhythmbox
2. connect to a DAAP source
3. look at year of track
4. check that DAAP source track has year encoded in it (e.g. check it in iTunes
or other rhythmbox source)

Actual results:
"Year" field is always "Unknown" even if the Year is present on the source machine.

Expected results:
The year should be filled in.

Does this happen every time?
Yes

Other information: