riak_core should not directly reference `riak-admin` commands in output

[russelldb]

https://github.com/basho/riak_core/blob/master/src/riak_core_console.erl#L179 and 9 other console output messages reference riak-admin. This is pretty confusing if you make a riak_core app that has nothing to do with riak, and try and use one of the console commands.

[slfritchie]

Time for some belated repo curating ... see incoming PR.

[jrwest]

work ongoing in #401 marked for same milestone (2.1)