Sign Pack Hot Reload Key Remapping Support and Minor Changes

[RavenholmZombie]

Changes

• Made it possible for players to remap the Sign Pack Hot Reload activator key.
• Added chat messages for when the Entity Class Renderer has been toggled.

[CSX8600]

Two things:

• I see this is actually the intended fix for Hot Reload Key needs to be remappable #78 . Can we confirm that the issue with non-US QWERTY keyboards was indeed the lack of ']' and not the lack of 'F3'? If so, then I'd be alright with that part of the PR.
• There's a ton of gradle changes in here I don't want to have made. I know at the time I think you were having problems with gradle but have since had it figured out. In that case, let's stick to the gradle setup we have and remove those changes.