GH-102 Address issues stemming from ANTLR's generated parser

- Addresses whitespace issue found when using compound Keywords such as NOT IN, IS NULL, etc.
- Removes flexibility associated with logical operators 'not in', 'is null',
   now required to be passed in as either 'NOT IN', 'not in', 'IS NULL', 'is
- Fixes Join condition exception message
- Fixes function expression param index update
- Removes old generated parser/lexer classes
- Adds new test cases