Documentation cleanup

Several warnings and errors were reported when building
documentation. This makes it difficult for developers to
validate that new changes to don't have problems.

Most of the warnings and errors are fixed with this change.

Change-Id: Ifb9edffce66dde27fbe72bb1ce1b997b041786ae
Convert Token KVS backend to new KeyValueStore Impl

This patchset converts the current token KVS backend to the new
dogpile.cache based KeyValueStore implementation.  The changeset
provides the same public interface as the previous KVS driver but
drastically reworks the internal mechanisms to be more similar to
the memcache based driver so that direct access to the in-mem db
is not required to effectively use the KeyValueStore.

KVS token backend is not deprecated anymore. However, it is still
inadvisable to use the basic-inmemory KVS backend for anything
outside of testing.

DocImpact

bp: dogpile-kvs-backends
Change-Id: Ib278636d4ffa3f7152287a48d02be598c50f698a
Merge "Documentation cleanup"