Supporting Tags - Improving abstraction between Riak and non-Riak workloads

The object tag "o" which was taken from eleveldb has been an extended to
allow for specific functions to be triggered for different object types,
in particular when extracting metadata for stroing in the Ledger.

There is now a riak tag (o_rkv@v1), and in theory other tags can be
added and used, as long as their is an appropriate set of functions in
the leveled_codec.

include/leveled.hrl

@@ -51,8 +51,6 @@
                         max_run_length :: integer(),
                         cdb_options :: #cdb_options{}}).                                               
 
-%% Temp location for records related to riak
-
 -record(r_content, {
           metadata,
           value :: term()
@@ -65,4 +63,4 @@
           vclock,
           updatemetadata=dict:store(clean, true, dict:new()),
           updatevalue :: term()}).
-          
+