docs.source.conf: Use capital letter to project.

Use `Avocado` to project name.

Signed-off-by: Ruda Moura <rmoura@redhat.com>
docs.Makefile: Rename arc to avocado.

Rename `arc` to `avocado`.
Plus:  change instructions for devhelp.

Signed-off-by: Ruda Moura <rmoura@redhat.com>
Merge pull request #163 from ruda/docs-devhelp

Build devhelp files for Avocado