rework the documentation

[kohlhase]

• build system (once that is ready)
• configuration (the old documentation is removed)
• replace all */mh/* URLs (they are different now)
• there must be more

[kohlhase]

in particular, rework https://github.com/MathHubInfo/Documentation/wiki/lmh to the new MMT version of lmh

[kohlhase]

I made a first pass over the documentation and removed the worst junk. This must suffice for the moment, until we have more to describe.

[kohlhase]

I am currently reworking the documentation to introduce the new concepts. This is going well.