TaskTree - make naming consistent

When extending the TaskTree, there are 3 classes involved:

1. For Task itself, e.g.:
   1. QtcProcess
   2. AsyncTask
   3. FileStreamer
2. For Task adaptor, e.g.:
   1. QtcProcessAdapter
   2. AsyncTaskAdapter
   3. FileStreamerAdapter
3. For Task shortcut (using declaration) in Tasking namespace, e.g.:
   1. Process
   2. Async
   3. FileStreamer

The suggestion is to drop the Tasking namespace and use this scheme:

1. For Task itself, e.g.:
   1. Process - this rename was already planed independently
   2. Async
   3. FileStreamer
2. For Task adaptor, e.g.:
   1. ProcessTaskAdapter
   2. AsyncTaskAdapter
   3. FileStreamerTaskAdapter
3. For Task shortcut (using declaration) in Tasking namespace, e.g.:
   1. ProcessTask
   2. AsyncTask
   3. FileStreamerTask