Improved error handling and tracebacks for modules

[Simon-v]

1) Catch and handle exceptions raised by error() and assert() within modules in the same way API exceptions are handled;

2) Increase the traceback depth of lua-related exceptions from 1 (the file and line directly raising the exception) to 3 (the caller of the function, which called the function which raised the exception, if applicable);

[epyon]

1) is implemented now