Tiny fix of where "refs" are set in TestValidate
Added new helper, new util function & corrected existing ones
Added cli executable to CMakeLists & created basic cli.cpp
Added cli include path to CMakeLists.txt
Refactoring of cli code to use module classes with common interface

Also added boost system & filesystem libs to cmake
Fixed boost bugs & made cli handle --help better & set opt/desc better
Made Validate cli module support no-errors & no-warnings options
Added string coverter for LinkType in Feature
Removed const-ness of "call" module method
Implemented YAML stream, Dump module & nix/base/types.hpp

The dump module now is implemnted and uses yamlstream to output all types of entities in yaml format. An additional nix/base/types.hpp with exactly the used instances of base templates has been created.
Fixes to match validation branch
Moved Dump code from header to cpp file & added documentation
Renamed "nixcli" to "nix" and cmake build target "nix" to "nixlib"
Merge pull request #313 from balint42/nixcli

Nixcli