Evaluator.java and CalculatorExpr.java cleanup

Bug: 21960281
Bug: 22047258

No substantive changes.

Reformat to 100 columns.

Correct and/or remove obsolete comments and occasional bits of clearly
dead code.

Better follow coding conventions.

Rename variables for both internal consistency and consistency with
other files.  This included a few renamings in Calculator.java
and CalculatorResult.java, and a comment fix in CalculatorResult.java.

Rename public fields per coding convention.  Correctly declare more
nested classes static.

Document FIXME issues to be addressed in followup CL.  This includes
a careful look at the msd computations.  I cannot construct any
failing examples, but I also cannot currently construct a correctness
argument.

Change-Id: I5c67493eeb7730edb4b3ca3ba1cb8b7d2b87dbc2
(cherry picked from commit abe2862b)