Networktask improvements

I've done some more NetworkTask improvements:

### unification ###
AnimeNetworkTask and MangaNetworkTask are replaced by NetworkTask, they where both doing the same except for the result. So this removes some duplicated code and also makes the handling easier as there is no ListType-check needed when creating a new Task (the ListType gets simply passed to the constructor).

### more flexible usage ###
As of #176 the result type of the NetworkTask is Object instead of ArrayList, this allows different results for different jobs. So GET and GETDETAIL now directly return an Anime or Manga object instead of ArrayLists with only one item.
Also additional data (like the page number for the paged lists or a anime/manga record for GETDETAILS) is now passed with a Bundle object to the NetworkTask constructor. This makes it more flexible for different taks and future additions and prevents multiple constructors.

### task cancellation ###
The current task is now cancelled if the user selects an other list. This avoids unnecessary computation of unneeded data and as side effect it fixes #190.
FORCESYNC-tasks are a exception for this: they keep running even if canceled and can complete the sync. Their results are just not shown if they are cancelled, but the sync gets done.