overhaul Readme.md, Dependencies.md, Platforms.md, andsoforth

[jgonggrijp]

In part these files have become outdated (for example because of changing insights), in part they have become redundant because things are explained better on the wiki, in part they will become outdated because of things that are still going to be written on the wiki. Therefore a general rewriting and slimming down of these documents is in order. I'm currently working on that in the update-docs branch.

[jgonggrijp]

This is basically done, it only needs to be pulled. See #38.