docs: include homing state diagrams in the Code Notes

Build-depend on graphviz, which provides dot, which converts diagrams
in .dot format to .png and .svg and probably other things.

Teach the docs Submakefile to auto-build .pngs and .svgs from .dots.

Include the existing homing state diagrams in Code Notes.

Ignore the newly generated .svg files.

Signed-off-by: Sebastian Kuzminsky <seb@highlab.com>
docs: better asciidoc dependency generation

This makes it accept both "image:" and "image::" for asciidoc image
inclusion.

Both are used as valid examples in the asciidoc docs, with no mention
of any difference between them.

Signed-off-by: Sebastian Kuzminsky <seb@highlab.com>
Fix motion-type docs in motion manpage

Signed-off-by: Chris Radek <chris@timeguy.com>
docs: add punctuation

Signed-off-by: Sebastian Kuzminsky <seb@highlab.com>
docs: don't call the HAL tutorial "Advanced", because it's the one to start with

Signed-off-by: Sebastian Kuzminsky <seb@highlab.com>
docs: this is more of a basic reference than a tutorial

Signed-off-by: Sebastian Kuzminsky <seb@highlab.com>
docs: clean up the Basic HAL Reference intro a little bit

Signed-off-by: Sebastian Kuzminsky <seb@highlab.com>
docs: minor reorg of HAL docs

Move the tutorial up, and the reference down.

Signed-off-by: Sebastian Kuzminsky <seb@highlab.com>