better overall structure, config in its own function
workings for #43 are in, seems to work well enough, and is general enough to work for any/all vars.
apply config read defaults after all args added, so defaults layer nicely
first step of #45, override file lookup moves to BURI_BASE/local/env/NAME/overrides.yml
second step of #45, move all key file references/generations to new local/env location, move roles_local to local/roles
adding disk type to labels for #46
Merge branch 'feature/config-file' into develop