Fix water level calculations when waterLevel > 127

This was caused by Java treating bytes as signed by default.

Thanks to @matt112986 for the research on this and for providing a test
map.

While fixing this, I also noticed that waterLevelSum doesn't need to be
a float.
Removing redundant super call

If a constructor does not explicitly invoke a superclass constructor, the Java compiler automatically inserts a call to the no-argument constructor of the superclass.
See the note at the bottom of this page: http://docs.oracle.com/javase/tutorial/java/IandI/super.html
Merge branch 'master'