Tweak to withdrawal amount logic

Rather than withdraw a fixed amount of n levels, increase the player's level by
that many levels.
Nano-optimization
Whitespace
Refactor listeners into single class; changes to come

We still need to clean up the code in some of the listeners, deduplicate some
things, and fix issues with detecting sign griefing.
Refactor griefing detection, among others; Fixes many bugs

This should resolve edge cases like signs on signs, etc
Refactor tracking of players removing signs
Clean up the calculator; naming, style, correctness, the works
Increment version to 1.3.8