Provide a minimal type for query_def.

query_def is specified across kv and repl, but the type no longer
exists, provided a minimal type to use for the meantime.  We can't use
typer to derive the type, because riak_index is so incorrectly
specified, typer believes all of the functions return no value.
Merge pull request #882 from basho/bugfix/csm/index-types

Provide a minimal type for query_def.