Removing fields from a map in Minilang clear-field

[Jonathon -- Improov]

I can't find any usage of ContextAccessor.remove(MethodContext) in Minilang's source codes at 
src/org/ofbiz/minilang/method/envops .

Shall I add an option to <clear-field> that will trigger a ContextAccessor.remove() rather than a 
ContextAccessor.put() that merely replaces a field with null?

I'm doing a custom service that <implements> an existing service in OFBiz, and I need to trim away 
the extra input fields before putting them to the existing service.

Jonathon