picasaweb: Add a picasaweb miner

https://bugzilla.gnome.org/show_bug.cgi?id=728878
Merge branch 'wip/picasaweb' of https://github.com/saurav-agarwalla/gnome-online-miners into wip/picasaweb

Conflicts:
	src/gom-gdata-miner.c
	src/gom-miner-main.c
	src/gom-miner.c
	src/gom-miner.h