Initial attempt to migrate wiki to readthedocs #434

Off the back of #434 I made some place holders for Installation Guide brought some info from readme in, but need to document PPA install process, and a full cmake build for Ubuntu for example. For the User Guide I started migrating the wiki content from http://www.zoneminder.com/wiki/index.php/Documentation. This is mainly to give a starting point for a new version of the documentation. No images included yet. Now starting to review and update to 1.27+