Add FREEZE and THAW methods for serialisation

[shawnlaffan]

Tests work with Serial, JSON::MaybeXS, CBOR::XS and CBOR::Free. (Edit: CBOR::Free was a false positive - it does not support FREEZE/THAW).

I also had a look at testing with some of the YAML modules but they do not support FREEZE/THAW callbacks.

Could probably be squashed into a single commit before merging, thus cleaning up debugging cruft.

Documentation is still needed. It should just comprise a note that serialisers that conform to Types::Serialiser are (should be) supported.

I'm not sure where to add it, though, as it does not fit under PDL::IO::Storable. Perhaps its contents could be shifted to a new PDL::IO::Serialisation or similar which is then loaded by default with the rest of PDL. That might be too large a change, though.

[coveralls]

coverage: 67.071% (+0.7%) from 66.357%
when pulling e60317a on shawnlaffan:freeze_thaw
into 0299134 on PDLPorters:master.

[mohawk2]

I feel like PDL::IO::Storable is a good place - it's just a vehicle to add PDL methods, which is what's needed here? Why do you say it doesn't fit?

Thank you for your great work on this! Could I ask you to add the doc notes you mention?

Don't worry about the commits, I'll do a squash. Could I also ask you though to put the tests in a section in t/storable.t instead of a separate file?

[shawnlaffan]

The reason for changing things is simply the general vs the specific. Storable is a specific serialisation method.

[mohawk2]

This is great - thank you!

[mohawk2]

I've rebased this, and had to make a couple of tweaks (see my commit changes - JSON::PP doesn't work). As soon as the CI blesses it, I'll merge it.

[mohawk2]

Thanks again! It looks like your repo has a number of branches you may not need anymore. Time for a spring clean? :-)