Ensure whitelist is a hash

[christophermaier]

The "whitelist" (despite the implication of the name) is a hash, mapping an easy-t-reference symbolic name to a complete command.

cc: @jtimberman @seth @jkeiser @scarolan

[seth]

:+1: LGTM. Is this something we should bake into the client as well?

[christophermaier]

@seth Adding a check when consuming the config file would probably be easy to do

[scarolan]

Thanks guys.