Dynamic API version

[stdweird]

The current has the API version harcoded via the distributed Net::FreeIPA::API::Data module.

It should be possible to use future, not-yet distributed features from newer API (or older API).
This can be achieved by fetching the API version and command data on demand, rather than loading it from the distributed Data module.

IN particular, this requires modification in
https://github.com/stdweird/p5-net-freeipa/blob/master/lib/Net/FreeIPA/API/Magic.pm#L135
(and a similar change for the version function in same module).

The code to retrieve the most recent version and accompanying commands is already used in gen_api, in particular https://github.com/stdweird/p5-net-freeipa/blob/master/gen_api/gen_api.pl#L50

Also the method to control the behaviour wrt the API version is required. Set the required version (default the distributed one), and control the fallback (if version X is requested and not avail by server, either fail hard or try the distributed version).

[stdweird]

@abbra this is what we discussed via mail (i think)