update to handle searching for mags on usenetcrawler

plus starting point for N newznab+ sites with an iterate over concept

breaks it down just a bit more
unit test starting for changes to provider.py

and there is alot to go here
final checks in merging usenetcrawler into newsnabplus querying.

TODO
- make changes to mag search to use new iterator method
- finally remove the usenetcrawler method fully
- put extra checks if no newznab is configured.
- reparse configuration file for list of newznab sites rather than keep adding global variables