Custom theme

Created by: seanmadsen

A CiviCRM theme for documentation with the following goals:

• display the version branch version (e.g. in user guide, show "4.6" or "latest")
• link to docs.civicrm.org documentation home page (to allow user to switch between books/versions/etc)
• link to civicrm.org home page
• colors/branding matching CiviCRM branding, to some degree (not aiming for 100% match here, but at least a little bit)
• more control over future theme-level features as needed

migrated from to-do list.