Several bugfixes (getpic.c, accepted but canceled issues, ...); Listing of available policies

- Bugfixes in fastpath/getpic.c (related to crashes since alpha5)
- Respect Content-Types of images in database
(needs database update, as Content-Type was incorrectly stored by previous versions)
- Typo fixed in help messages
- RSS-Feed (currently only after manual authentication while session is valid)
- Listing of available policies
- German translation fixed: "gebe" -> "gib" (Imperativ)
- Bugfixes related to issues which had been accepted but canceled afterwards
- Prohibit creation of initiatives in disabled areas or with disabled policies