Rename "rotate*" fields.

Owing to the Python language spec, Jython cannot distinguish between
fields and methods that share the same name. NavigatedDisplay extending
DisplayMaster results in Jython essentially overwriting
DisplayMaster.rotate*() methods with NavigatedDisplay.rotate* fields.

The end result is that the rotate*() methods can no longer be called
via Jython (used in conjunction with setting the
"python.security.respectJavaAccessibility" property to false).

The most straightforward fix appears to be simply renaming the fields.
Improving comments.
Merge pull request #40 from jon4than/jython_field_conflict

Renaming NavigatedDisplay's "rotate*" fields.