Worker wrapper cmd

Runs the worker wrapper as a command line program. This change is pretty simple
is just parses the input parameters and interfaces with baseworker-go. Most of the
logic is handled by the corresponding package.
What about things like config parameters that are constant for a worker (e.g. CLEVER_API_BASE)? Do we envision still handling those through the environment, in which case the wrapper needs to pass it's environment to the spawned process (might already be done by default)? Alternatively, we could make those command line flags that the wrapper passes through.