CAPX-17 - New Mapping Button

# Ready for review
* Added create new mapping button and help text. 
* Broke out pages into their own file.
* Added button class to links so that they look like a button.
In general it's recommended to have one form for create/update operation for the entity and I don't see any issues here to two same forms. Even so stanford_capx_admin_config_mapper_new() and stanford_capx_admin_config_mapper_edit() is just a callbacks, we can use only one for both cases.