add initial tests for coercion per attribute

Completely not comprehensive, and uses the older hashref syntax.  This is, at
the moment, more to check that the warning MXCPA issues now than anything
else... But will be a good point to start at when incorporating the MXCPS
functionality directly.
evil, evil, evil hack...

Work around the warning introduced by MX::CoercePerAttribute by localizing
warnings into nothingness around _process_coerce_option().
v0.020_01

	* Keep MXCPA quiet, for now.  This is evil (hence the dev release), but
	  should keep things status-quo until we properly integrate MXCPA
	  functionality into MXAS proper.