Upgraded to latest NUnit.Framework and ExtCore versions.
Fixed some unit tests so they at least compile (though many are currently failing). In particular, the SLanguage tests now compile, though many of them are failing due to a parser issue.
Reorganized SLanguage test cases (for printing and parsing) to use TestCaseSource, so it's easier to see which tests are passing and which are failing.
Fix 'showPat' so it prints correctly when the parameter list is empty.
Moved some errant characters -- no functionality change.
Cleanup, simplification, and reorganization of parsing code. The parser doesn't yet handle let-bindings correctly, so it fails fatally when it encounters the "let" keyword instead of backtracking and parsing the keyword as a variable.
Implemented parsing for Let bindings.
Fixed the way rules are printed so they always end in a semicolon (as opposed to separating multiple rules with semicolons).
All parsing and printing test cases now pass. However, some more complex cases in the other test fixtures don't appear to work correctly -- they should be added as test cases for parsing and printing.