Set Swift operator role to a more likely default
Refactored file reading paths
Refactored argument checks and defaults
Separated override argument parsing

Added error handling and friendly error messages.
Keep track of options defined by user

Options defined by user should not be overwritten by other functions.
Fix Swift
Refactored cli_dir setting
Attempt to find cli_dir even if it's already set

This is the behavior of all other options. Thanks to TempestConf.set(), it will
not overwrite it if the user specified it.
Minor fixes in horizon discovery
Move do_resources to configure_tempest