Keyboard mapping

Hi Steven,

Do you remember issue #10?
https://github.com/caron/PyQtForSoftimage/issues/10

Today I have finally given it a try, the keyboard mapping dictionaries are now submodules of the key_mapping package. There are also some functions to list/get/set the language on key_mapping's init file, a new softimage command exposing those functions and a json file where the preferences are stored.

You have to restart Softimage in order to use different keyboard mappings (modules get cached by python), the french mapping is a copy/paste of https://github.com/caron/PyQtForSoftimage/issues/10#issuecomment-16238773.

Do you think it worth the merge?
Cheers!