Feedback Custom Processor hook needs some work

Hiya,

the ability to add custom processors is excellent. I was planning to author a nice universal "drag" that used coroutines to create that drifty style of axes in the old system. Figured newbies might find it helpful (and it'd be useful for my own ends) but unfortunately the processor method only seems to pick up key-down and there doesn't seem to be any support for when the key is released.

in a nutshell, I really really think the processor should be able to perform actions against release behaviour as well.