unify how parameters are shared with pftool and targets

[tomeichlersmith]

• reorg YAML configs in config dir to be more clear about different config's purposes
• drop RcFile
• load YAML into Parameters that are more strictly typed than YAML::Node
• recurse into sub-files that are marked with the !file YAML tag
• move some pftool command line arguments to configs, open door to provide more detail about what boards are connected via YAML config
• did not pass Parameters into pflib::Target constructor (which is what I want to do) to avoid conflict with Target Jeremy is developing
• drop loop over multiple hostnames

To Do

• rebase onto main after a first draft of the Bittware Target is implemented and refactor to prepare for Ecal classes #255
• ~update to pass Parameters into pflib::Target ~ not doing to avoid hiding the named (required) arguments
• include a boost::python::dict -> Parameters conversion for pypflib not doing here, but probably can do