Update docs. Correct errors reported by setup.py build_docs. Add rest interface and link to rest doc to features page. Add link to xmlrpc doc to features page. Add rest doc to index. Update rest doc, hopefully clarify confusing use of parameters in patch action section. Fix code examples in "Adding new rest endpoints" section. Fix example adding import of exception.

[run]

# ignore the dist utils. They are not part of the code base
# we are going to test. They are used by maintainers only.
omit = roundup/dist/*