Tests for argument conversion of Python bindings generator
* Tests for parsing elemental types from Python bindings
- Add positive and negative tests for int, float, double, size_t,
const char*, bool.
- Tests with wrong conversion behavior are skipped.
* Move implicit conversion of bool to integer/floating types to wrong
conversion behavior.
* Add Python support for error message handlers.
* Move the static variable to the only function that uses it.
* Remove the optional param (user data), since this can already be handled by closures.
* Correct the help string.
* python: added redirectError test
