Fixed some javadocs.
Clarified some comments.
FlatRegionApplicator -> FlatRegionVisitor.
Added CombinedMask(Mask ...mask) constructor.
Added BoundedYMask that requires that Y is in a range.
Added FuzzyBlockMask, which uses BaseBlock.containsFuzzy.
Added BlockCount, which counts the number of blocks matching a mask.
Aded BlockReplace, which replaces blocks with a pattern.
Added various visitors (BFS, Downward, Recursive, Region).
Added OperationHelper.completeBlindly().
Changed //count, //fill, //fillr to use visitors.
Added Guava... for now.

We have to check to some serious breakage across the board before we can
release.
Changed /remove[above|below], //set to use visitors.
Added FuzzyBlockMask(BaseBlock... block) constructor.
Added RegionMaskFilter to filter a RegionFunction.
Converted /removenear, //replace to visitors.
Made CuboidRegion(world, ...) constructor clamp to world.
Made CuboidRegions in EditSession clamp Y to world.
Changed //center to use visitors.
Moved visitors to com.sk89q.worldedit.visitor.