Add riak-cs-debug

Add riak-cs-debug to gather information for troubleshooting. Most part of this is a copy of riak-debug.

gathering info:
- logs
  - access.log
  - console.log
  - error.log
  - crash.log
- configs
  - app.config
  - vm.args
- system command results
- riak  command results
  - riak-cs-gc status
  - riak-cs-storage status
  - riak-cs-cinfo

_This PR was extracted from #826._