Android integration

Added android contact integration ( RetroShare contacts display on android contact list )
To make this possible a lot of change on the code had to be done, with the benefit that now more server are supported in parallel.

Missing some cleaning on MainActivity

This pull request is more aimed to call electron attention that to be really merged, and to ask to you that if you do further development please take in account this clone with new features otherwise future merge will need a lot of work...