doc: update SAPI

Update Quartus section and fix some formatting issues.

Signed-off-by: Franck Jullien <franck.jullien@gmail.com>
doc: fix CAPI syntax and does cleanup

As this, capi.txt cannot be convert by asciidoc.
Also fix some formatting problems.

Signed-off-by: Franck Jullien <franck.jullien@gmail.com>