allow warning generation for non-whitelisted options

allow warning generation for non-whitelisted options

The idea is simple: Each¹ Find*( call starts with a call check if the
given option (with the requested type) exists in the whitelist. The
whitelist is specified via our configure-index file so that we have
a better chance at keeping it current. the whitelist is loaded via a
special (undocumented for now) configuration stanza and if none is
loaded the empty whitelist will make it so that no warnings are shown.

Much needs to be done still, but that is as good a time as any to take a
snapshot of the current state and release it into the wild given that it
found some bugs already and has no practical effect on users.

¹ not all in this iteration, but many