[doc] complete rewrite of index.rst

Which had to be done, because the changes to the old version were just way too
big.

Also see Github Issue #26.

Signed-off-by: Erik Bernoth <bernoth@dresearch-fe.de>
[doc] renamed test-framework to api-docs

This is merely a file move. Yet that is not the end to those changes. There
should be a better solution with the autodocs, which might not look that handy
but should be much more usable and adaptable to structural changes which are
very likely to come in the future.

For now this change is added to Github Issue #28.

Signed-off-by: Erik Bernoth <bernoth@dresearch-fe.de>
[doc] new page getting-started

Added a page that explains a MONK user what he can do with MONK.

Belongs to Github Issue #27.

Signed-off-by: Erik Bernoth <bernoth@dresearch-fe.de>
[doc] new file contributing

which describes the development process and ways to interact with the
MONK community.

See Github Issue #28 for more info.
Also some of the changes are more about the policies, thus look at Github Issue
 #30 for more details.

This change also includes the changes from Github Issue #21, which added some
info about the environment variables configuration to the old docs.

Signed-off-by: Erik Bernoth <bernoth@dresearch-fe.de>