Turn the keyboard class backing the km_kbp_keyboard and km_kbp_keyboard_attr objects into just keyboard_attributes.
Move the abstract_processor and sublcasses as the objects that back km_kbp_keyboard and make keyboard_attrs a member of the asbtract_processor.
Move kmx_processor and mock_processor declarations into their own headers.
Make all vector<km_kbp_option_item> into vector<option> to handle memory management, moving and copying correctly.
Update test cases accordingly
Templated convert for going between any combination of UTF codecs with
an identity function specialisation for when src & target forms match.
Includes implmentations of json and basic_ostream << operators for
u16string & u32string.
