Some more debug on the numeric expressions. Another note I didn't mention
specifically. Most of the expressions treat null contents as false, or a 0 as false,
If you have a string that contains a character that is not 0-9, and wish to feed that
to a numeric operation, like multiply or subtract, then it will throw
and error upon evaluation. The one exception to this rule is the + operator, which
will, when both args are NOT numeric, then it will simply concatenate the two strings.

And, if you wish to include an arithmetic expression in the filelist, then
wrap it in parens. Arithmetic expressions are now allowed in the ranges (as you might expect.)

I cleaned up en and en_US, and added en_US_test for the test cases.

I have yet to remove some debug from the source... Maybe by next commit.