Port buildlogic from WorldEdit

[aurorasmiles]

This tries to port the current build logic from WorldEdit to WorldGuard. The project compiles fine, and the jars look similar enough from a quick glance. Limited testing in Minecraft showed no apparent issues. The only differences I've noticed:

• pom of prtree/flyway-core no longer in META-INF
• some bstats classes no longer included
• some flyway classes no longer included

Notes:

• Piston stuff is currently commented out, but I decided to still leave it in - should make transitioning easier at some point
• I've commented out -Werror in the compilerArgs for now - ~~suppressing~~ addressing all of the deprecation warnings should be a seperate PR
• Something else that still needs to be ported are the checkstyle changes, but again, not here
• There might (read: probably will) be some WorldEdit stuff leftover that isn't required in WorldGuard, even though I went over everything multiple times