Mapping of action names to actions.
By default, actions are looked up in a controller class by index. Sometimes, it's not possible
to create such an index, such as when the desired index is a reserved word like 'object', or one already
present in the controller but with a different purpose, like 'start'.
An entry may be placed in this mapping and it will be used as though there were a class member with the same name.
The presence of an entry in this mapping for a given action will take priority over any action
defined within the controller class.