Rustpkg run cmd

Move some code from rustpkg::lib.rs to rustpkg::run_cmd.rs and rustpkg::perform.rs

* run_cmd::run_cmd(command, args, context) acts on on parsed command line parameters to build, install, info.. etc.
* perform::build() and perform::install() does the actual work of installing and building (Here is room for more cleanup)
* build_context is initialized a little later in the build process. (Don't initialize it if we just want to run info)
* The trait CtxMethods is removed