Add #riak_core_fold_req_v2 record, part 1 of 2

Move definition of ?FOLD_REQ to v2.

Add functions to riak_core_util.erl to create v2 versions of the
record: arity 1 (upgrade #riak_core_fold_req_v1 record to the v2
record), arity 2 (args = the two record elements of the v1 record)
and arity 4 (args = the four record elements of the v2 record).

Disable request forwarding in riak_core_vnode:forward_or_vnode_command()
if the request explicitly contains not-forwardable annotation.
Add riak_core_capability handling for fold requests
Fixes #189 -- include socket peer info in lager messages
mark AAE vnodes as internal databases for leveldb flexcache accounting
Refactor make_fold_req(), add make_newest_fold_req(), add EUnit tests

Partially addresses https://github.com/basho/riak/issues/407 ... a patch
to riak_kv is also required.
Sort AAE differences before acting upon them via read-repair

Apply patch to hashtree.erl that was developed for
https://github.com/basho/riak_kv/pull/646.
Use inet_parse:ntoa/1 for peer addresses
fold unnecessary make_fold_req2/4 into make_fold_req/4

also renamed make_fold_req3 to make_fold_reqv, since the 3 didn't make
sense any more, but it's still nice to have the name slightly different
than the exported functions

also fix a bit of doc
Merge pull request #400 from basho/gh189-handoff-sender-info

Fixes #189 -- include socket peer info in lager messages
Fix use of removed hashtree:compare/3
Merge pull request #411 from basho/slf-aae-sort-difflist-hashtree-moved

Sort AAE differences before acting upon them via read-repair
mark AAE vnodes as internal databases for leveldb flexcache accounting
Merge branch 'mv-flexcache' of github.com:basho/riak_core into mv-flexcache
Merge remote-tracking branch 'origin/slf-vnode-ops-opts' into develop

Conflicts:
	src/riak_core_util.erl (fixed -SLF)
move ebin/riak_core.app to src/riak_core.app.src
refactored riak_core bits of the schema in here, with tests
minor changes based on PR#417
Merge pull request #417 from basho/jd-cuttlefish

refactored riak_core bits of the schema in here, with tests
Merge pull request #416 from basho/move-to-app-src

move ebin/riak_core.app to src/riak_core.app.src
Merge pull request #408 from basho/mv-flexcache

mark AAE vnodes as internal databases for leveldb flexcache accounting