make riak_kv_test_util app startup less brittle

In commit c3ebdc9 I added some missing apps to the list of apps in
riak_kv_test_util that need to be started for some riak_kv
testing. Unfortunately trying to list out the entire app dependency tree in
that module is very brittle and is to easy to forget to update if a new app
dependency is added in the future. Modify that list to eliminate the lower
level apps and instead just list the obvious higher-level apps, and add a
new function that starts each application's dependencies before starting
the app itself. Also change the riak_kv_test_util setup function to return
the list of all apps started, and change the cleanup function to take that
list of apps and stop them all.
Merge pull request #733 from basho/vinoski/app-startup-for-tests

make riak_kv_test_util app startup less brittle