Create an umbrella KETCube webpage

[belohoub]

Create an umbrella webpage with basic information about KETCube. Today, this task is concentrated to the KETCube-docs repository, but repos are Work-In-Proggress.

Currently we have inconsistent content in KETCube-docs and KETCube-fw (and other repositories), as the KETCube-fw contains features still undocumented on the top of KETCube-docs. Naturally, one should take KETCube-docs 0.1.1 and KETCube-fw 0.1.1, but taking repository top(s) is the first idea for many users...