added gpodder package

Hi,

I added a gpodder package. Please keep in mind, this is my first package. So if something is not optimal please notify me and I happily fix it.

Best,
Sven
If `GPODDER_HOME` is not set, it defaults to `~/gpodder` and `GPODDER_DOWNLAOD_DIR` defaults to `~/gPodder/Downloads/`