A module can register a function to a domain. These function can then be
called by external actors enabling the modules to expand their
functionality beyond the module API. Each module should use its own domain
e.g the library name.
Currently, the functions do not return results. The possible next step
would be to alter the function entry point to return a result set of
sorts. This would allow the modules to convey structured information to
the client information which would handle the formatting of the result.
Although this sounds good, it is not required for the implementation of
MXS-929.
