[Forge] Change compareTo() for commands to fix a Comparable contract issue.
Clean up Javadocs for the blocks.* package.
Code clean up, add preconditions, and correct Javadocs.
Merge branch 'master' into feature/multipass

Conflicts:
	src/main/java/com/sk89q/worldedit/extent/buffer/ForgetfulExtentBuffer.java
	src/main/java/com/sk89q/worldedit/internal/expression/runtime/Sequence.java
	src/main/java/com/sk89q/worldedit/math/convolution/LinearKernel.java
	src/main/java/com/sk89q/worldedit/math/transform/AffineTransform.java
	src/main/java/com/sk89q/worldedit/regions/FlatRegion.java