Added support of custom RSS services compatible with Google Reader API

[Alkarex]

Hello Sun Zheng, In the process of enabling an API compatible with Google Reader in the FreshRSS project (fully Open Source), I have forked EasyRSS in order to add a way to customize the service used instead of the hard-coded google.com.

The goal is twofold:

• To improve the quality of the Google Reader API in FreshRSS https://github.com/marienfressinaud/FreshRSS/issues/443 by testing it from different clients
• Potentially to revive EasyRSS by offering a completely Open Source client that works with different RSS services, FreshRSS being one of them.
  • That is also the reason why I have removed a bunch of permissions and Google Analytics, to differentiate better from the other clients available.

This pull-request is mainly to initiate the conversation and hear if you could at all be interested in such a thing.

I look forward to reading from you.

Best regards, Alexandre

[Alkarex]

@simongray: Måske kunne det her også have din interesse?