The documentation here had a number of problems, namely: it included
receiver documentation, it repeated itself in a number of places, and
its structure didn't lend itself to give an easy read.

This commit removes all receiver-specific documents, reduces
repetitions throughout the documentation, rewords a number of paragraphs
to be a bit more formal, and improves the overall structure of the
documentation, including proper links to other projects.

This work is part of YAN-979

.

Signed-off-by: Rodrigo Tobar <rtobar@icrar.org>