More camelCase -> underscore in terminal.py

Let's hope this is the last of them...
Removed all GUI from kalpana, expanded pluginapi

Refactored save/new/open-functions in kalpana.py. Raw (output-agnostic)
functions are now called *_file(), while those called from hotKeys and
Terminal are kalled *_k() and *_t() respectively (in the cases that they
exist).

Also:
* Changed prompt_error to error in kalpana.py
* Added save, open, new, quit to callbacks for plugins
* Updated plugin_docs with new commands
* Removed unused gui-import in imports.py
Removed guidialogs options since it does nothing

See #28