* trimmed fat from cyclus.rng.in
* finished rng cleanup. Modified xml_file_loader to build/initialize from new schema paradigm
* fixed rng problems by adding fac,inst,reg specific optional content. fixed init errors by adding InitFrom to reg and inst classes. other minor fixes
* added missing member far to facility model initfrom
* tmp - refactoring xml file loader
* refactor - flat loader is subclass of regular loader
* added cli flags for toggling flat schema and for manually specifying schema file.
* doc comments and style tweaks
* fixed unflag schema paths var init
* renamed builder member var and made it protected so that subclasses can copy it in their InitFrom method for proper cloning