POM: make the description better
OpService: check for matching argument count
OpService: use canConvert(Object, Class) for now

Eventually we want to use the canConvert(Object, Type) signature,
once it exists, but for now we use what we can get.
OpService: use "run" for executing an op by name

This is consistent with the other run methods of OpService, as well as
those of other related services such as CommandService & ScriptService.
OpService: fix style
OpService: add missing section header
Fix copyright header descriptions
Add project license
Add interface for testing contingencies
OpService: improve lookup and run methods

The lookup method now skips Ops that implement the Contingent
interface and return false for conforms() with the indicated inputs.

The run methods have been reorganized to be better.