Modify actions per file/subdir in file tree.

[brenthuisman]

Requires fancier file tree view (i.e. the file tree below action categories).

[brenthuisman]

Fancier means an actual tree view (so actions can be modified per subdir in addition to per file).

I think the way to implement it is to move files between the file lists (e.g. self.create, self.verifiedfiles_err,self.verifiedfiles_repairable), or get rid of those lists and use something like the table shown in the GUI also in the par2deep class: associate an action to a file, which can be modified. Looping in the execute function then just need to filter instead of using the dedicated list.