Tests for 'execute' + some new function names.

Renamed 'prompt' and 'set_prompt' to the more intuitive names 'prompt_visibility' and 'prompt_text'.
Implemented 'exec' and changed name of two functions.

Altered the names of 'prompt' and 'set_prompt' to the more intuitive names 'prompt_visibility' and 'prompt_text', respectively.
Stripped of initialization code.

This file should only contain command definitions.