Rework Readme.md

[defvs]

Some informations on it are old, deprecated. Most of the screenshots are not representative of the current program.

[xeruf]

Please add some more details about what you consider "deprecated" information. Is it just about the features?

[defvs]

I'll wait until my branches are merged and I'll do a readme overhaul, and a video tutorial.

[defvs]

Deprecated :

• Connect.sid (now with the login dialog)

• Most of the screenshots have changed since (the downloader is very different)

• Some gradle tasks are missing

• gradle.properties should be explained

[xeruf]

What should be explained about gradle.properties? Which relevant gradle tasks are missing?