cbc: Use the newer callbacks API

Change-Id: Ie0943e252b3ccba4982cb0189ce7669a53ed3dd9
netbuf: Fix curblocks/maxblocks

We previously didn't use these variables resulting in high amounts of
malloc/free.

Change-Id: Iaeae2f462d93707f3baec286c6231529d191c95b
api3: Remove lcb_CMDOPTIONS

Let all the options be at the same level, this lets us better optimize
the layout.

Change-Id: I4b81b35c0d68b01d8f2cb3731808d4836ba8e46d
Better document v3 API

This reworks the entire api3 file (but not changing anything else in the
code) by reorgaizing the sections of the file. It also moves the more
low level buffer stuff to kvbuf.h.

Change-Id: I765b18a410c2591edecd61040e96c1d6fb16b4b5
api3/touch: command is const

Change-Id: Ie8f6c16d3a80d72d45046c8f3507a8a8ace9b51e
Populate 'bufh' in get responses

This forms the basis of "Futures" for gets

Change-Id: Ifec6416601b489eb3151a69f098910535d217c8e