* 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
Merge pull request #683 from rwcarlsen/simple-input

Simple input
added an exclusivity flag and updated test case 2. tests fail as expected
updated case3, all expected failures occur
updated case4, all expected failures occur
updated case5, all expected failures occur
updated case, all expected failures occur
updated case7, all expected failures occur
added requester-specific exclusivity for greedy resource exchange
added exclusive arc translation and an appropriate test