Ignore *.pyc
Lots of changes!

--.per file to yaml (should probably match .fpg format)
--Include source file paths in .per and add support for multiple
pieces of distinct used IP.
--Gather source file list in Toolflow, then pass this in one chunk to
ToolflowBackend right at the end.
--Removed any control the frontend has over the middle. Eg, don't
wait for the frontend to say where the .per file is, just tell it
where it should go.
--Added many docstrings, to shortly be sphinxified
Added sphinx documentation

Added some auto-generated sphinx documentation
(see _build/html/index.html).
Much more to do still...