Initial pass at Bucket Type documentation
- Also clean up build warnings from sphinx
Add security section
Add in Yokozuna maintenance functions
Add initial Datatype (CRDT) documentation stubs
Checkpoint Bucket Type and Data Type docs
Checkpoint Security documentation
Checkpoint Yokozuna docs
Checkpoint Deprecated features
Updated to reflect @seancribb's first round of comments
Fix syntax on a few examples so pygment will parse properly
Fix security docs: syntax highlighting and renamed user to riakuser
Move deprecated features into clients; remove deprecated page
Clarify RiakBucket.new() and move search shortcuts to deprecated
Clean up the deprecated warnings
Add stream closure warnings to streaming methods
Add a couple of comments to the Query documentation
Address review TODOs:

* Map documentation includes reload/update, duplicated from the parent
  class.
* The section titles are too monotonous and not descriptive enough.
Tweak the Set class documentation.
Fix verbatim text in Set documentation
Expand section about sending operations to include examples of how to
do so.

Also tweak the context/OR section to link to the relevant methods on
datatype classes.