Stop user input for Constants from propogating

[MatLomax]

Need to figure out how to show a textbox and use the user-inputted value when right-clicking on a value-settable device.

[MatLomax]

It now takes a value, but the keypresses are not being blocked, triggering unwanted behaviour.

[MatLomax]

With the addition of Main.blockInput = true; it blocks letters, but numbers are still propogated (resulting in changing held inventory slot).