[Kget] Reworked Default-Folders

[Lukas Appelhans]

Hey!
The last days/weeks I've reworked the default folders stuff as suggested by 
FiNeX...

Now it is:
-default folders per group
-removed generic default folder + folders per dir
-removed complete "Default Folders"-Tab in Config-Dialog -> options are now in 
GroupSettingsDialog
-for setting a generic default folder just use * as regexp...

I hope everyone is fine with those changes... additional things to be done 
after this patch are to rework the group-status-things... FiNeX, do you have 
any idea to do that?

Additionally we could think about ungrouped transfers... 

Lukas