New FimFiction.net API downloading:

- the new class FimfictionApi can download stories from the new API
- it will only do so if a token (or a client key/pass) is conigured
- Cache was adapted to use directories (shorter filenames)
- Cache now supports GET/POST parameters
- Cache now supports OAuth2 (enough for Fimfiction new API)
- Debug mode will now output cache hit/miss on stderr