This commit contains the following:
* New data types to support full tracebacks
* New traceback data type used across stl and ast
* Updates to tests
* fixes for error messaging in sym and some stl functions
* clean up all tests
* bugfix for zero value functions, and test
* removed expand function, put in snippets
* added doc strings to Symbol type
* added doc strings to symbol declarations
* implemented display for Args type
* wrote a help function
* wrote docstrings for all builtins and config vars
