Add application specific/development codecs

[Kubuxu]

trafficstars

For dev purposes, it is good to have a range of valid codecs that can be used for developing support for new protocols. I think we had something like that in the past but I can't find it in the table right now.

[victorb]

Just came up regarding IPLD resolvers as well, when you want to have a custom codec. We should have a range people can chose in between and be sure we want add something to the table to overwrite it.

cc @vmx

[eikeon]

Duplicate of #39