Extract common api call behaviour

[vduits]

With adding the IGDB API in sight we want to extract common api call behaviour into a new class. There are some similarities with twitch, but the rate limit system works differently and its ties should be omitted where possible.

• [x] Create new service for the connection handling for both twitch/igdb with a good name.
• [x] Extract buildconnection, addHeaders and readresponse from TwitchApi.
• [x] Extract the twitch ratelimit parts from readresponse, for example by returning a new pojo with the body and headers that the higher level service can work with (in this case TwitchApi.request)

[PS2emu]

I can complete this issue by mid-to-late week.

[vduits]

Alright good luck, let me know if you have any questions.

[vduits]

Thanks for helping out.