update README

#### Actu:

This branch has merged the apps branch.

This branch is up-to-date (2018-08-20).

___ /!\ This is not the current version used in build. /!\ Please check "Apps" branch or "Authentification" branch. /!\ ___

#### TODO:

This is the current Goal List:

+ Fully integrate into Account Manager:

	- Add fake content Provider

	- Check that account of type "at.bitfire.davdroid" works

	- Replace usage of setup activity

#### TODO:

This is a list of thing to do:

+ Fix issues:

	+ issue # 0 : App's crash with dav query that are too long to finish

	+ issue # 2 : When setup's activities is killed, it also kill the services in background

	+ issue # 3 : Synchronisation rythme doesn't run as expected (too long and too spaced between two synced)

	+ issue # 4 : If a folder declare to be synced during setup is removed and then re added, it won't be sync again.

+ Prevent failure due to service stopping, or internet connexion lost

+ Sync settings

+ code cleaning and rewriting

+ Use Eelo Account instead of raw credentials