Clean up MaaS README.md
Clean up MaaS README.md

This commit cleans up maas/plugins/README.md by doing the following:

* sets proper capitalisation on headings
* uses lists for lists of items (which are currently all being printed
  to the same line)
* makes subheadings more consistent throughout

Closes issue #429

stevelle/rpc-openstack,git-harry/rpc-openstack,darrenchan/rpc-openstack,robb-romans/rpc-openstack,major/rpc-openstack,cloudnull/rpc-openstack,xeregin/rpc-openstack,galstrom21/rpc-openstack,xeregin/rpc-openstack,busterswt/rpc-openstack,jacobwagner/rpc-openstack,miguelgrinberg/rpc-openstack,xeregin/rpc-openstack,busterswt/rpc-openstack,sigmavirus24/rpc-openstack,stevelle/rpc-openstack,sigmavirus24/rpc-openstack,mancdaz/rpc-openstack,andymcc/rpc-openstack,prometheanfire/rpc-openstack,jacobwagner/rpc-openstack,busterswt/rpc-openstack,miguelgrinberg/rpc-openstack,miguelgrinberg/rpc-openstack,major/rpc-openstack,byronmccollum/rpc-openstack,rcbops/rpc-openstack,claco/rpc-openstack,darrenchan/rpc-openstack,prometheanfire/rpc-openstack,mancdaz/rpc-openstack,galstrom21/rpc-openstack,sigmavirus24/rpc-openstack,BjoernT/rpc-openstack,git-harry/rpc-openstack,stevelle/rpc-openstack,byronmccollum/rpc-openstack,cfarquhar/rpc-openstack,byronmccollum/rpc-openstack,cloudnull/rpc-openstack,BjoernT/rpc-openstack,robb-romans/rpc-openstack,claco/rpc-openstack,claco/rpc-openstack,sigmavirus24/rpc-openstack,andymcc/rpc-openstack,xeregin/rpc-openstack,hughsaunders/rpc-openstack,cfarquhar/rpc-openstack,darrenchan/rpc-openstack,darrenchan/rpc-openstack,shannonmitchell/rpc-openstack,hughsaunders/rpc-openstack,andymcc/rpc-openstack,shannonmitchell/rpc-openstack,rcbops/rpc-openstack