GitLab

Renaming doc files to make the file names more palatable and in preparation for including documentation in sync process

Removing make and automake. The only supported build systems are Bazel internally and CMake community supported

Added a missing newline

The Optional() matcher is otherwise undocumented except in the source.
This patch adds it to the cheat sheet for better visibility.

Removed "Documentation.md" not adding value and not consitent with internal docs

Rename AdvancedGuide.md to advanced.md and adjust the links. 
Part of documentation rationalization work

move only types docs

Per the review comments.

The documentation of former versions is available in the history (e.g.
by checking out the appropriate git tags), so there is no need to keep
them in parallel to the current documentation.

The document itself uses lambdas later, all the scaffolding to
work around lack of lambdas should be considered for removal, but
that is much larger an effort than I can commit to.