Changes for issue #20 (and/or vs <,=,> precedence) and issue #6 (ELSE operator)

This seems to fix the issue, and I've tested that my old code still works as well as that this now works:

print 2 >=1 and 2 > 1.
True

And the previous behavior can be forced with parentheses:

print 2 >= (1 and 2) > 1 .
False

The actual human-made changes were changing three expression lines in kRISC.tpg and then also having to change one line in Compiler.cs because the name of an expression changed.  (It no longer made sense to continue using the same names when a new sub-expression for comparators had to be made).

All the rest of the changes that github claims, for Scanner.cs, Parser.cs, and ParseTree.cs are just the effect of running TinyPG and are not part of what I actually edited.