Split svtplay-dl to modules

This is my ambitious attempt to split the script in to several modules.

I have tried to make sure that all changes on master between the time i branched off and now have been applied, but please make sure for yourself.

I have had very limited possibility to verify the functionality of the program; I only use a fraction of the services myself. SVTPlay, URPlay, Expressen and RUV should work at least.