Allow shift+click toggle for shotgun pumping like the Sentinel

[HalfdeadKiller]

Summary (a quick, 2-3 sentence summary): Add a toggle, similar to the sentinels spit, for shotgun pumping. This would allow us to either use a macro, or the verb, or shift pump. And also allow us to easily examine the shotgun to see shells left.

Benefits (How this will benefit the server and game as a whole): See Summary

Details (Description of how you think this would work, the benefits, etc): See Summary

Implementation (Optional, if you have an idea how to implement it): Code