Capability checks for very old capabilities

[martinsumner]

The riak_kv code has multiple capability checks (cluster-wide checks that all nodes support the capability) for capabilities that have existed since Riak 2.0 or before.

Capability checks are cheap, but not free. There are two capability checks in every encode_item call for handoff - so they may be called 1000s of times per second.

There has been anecdotal evidence of situations where during node failure events capability checks have reverted back to old capabilities - and then caused unexpected behaviour - in particular with the object_format capability check.

For 3.4 - we should sweep through these old capability checks and remove, default to the expected capability.

[martinsumner]

https://github.com/OpenRiak/riak_kv/tree/nhse-034-orkv.i57-fixcapability

[martinsumner]

#26