Remove 3rd dimension of POST data by directly accessing request data - a simple EpisodeActions array has to be posted now. This way the api is closer to gpodder.
Additionally, removed EpisodeAction upload as String, so it's now incompatible with older versions
Parsing EpisodeActions from String can lead to problems if the String is changed by only a little bits.
Additionally, the gpodder api describes the upload as Array.
Uploading EpisodeActions as String is still possible.
EpisodeAction/create now can deal with multiple EpisodeActions inside a single EpisodeAction string, they will be processed one after another.
For this EpisodeActionReader->fromString() now returns an array of EpisodeActions.
