Ability to parse multi value -c arguments on the commandline

Hi!

The following patch enables lists of values to be parsed on the CLI via the ```-c``` argument.
This way one can configure Nimbus and Supervisors almost entirely from the CLI.
It is fully backwards compatible and only provides better parsing logic to distinguish keys from lists of values.

Sample:
```
bin/storm-mesos nimbus -c java.library.path=native:/usr/local/lib,mesos.master.url=master1:5050,mesos.executor.uri=http://mydomain.com/storm-mesos-0.8.3-wip3.tgz,nimbus.host=myMaster,storm.local.dir=../storm-local,ui.port=7070,storm.zookeeper.servers=zk0,zk1,zk2
``` 

We use it to run Storm on Mesos, but the patch is generic and benefits regular Storm CLI parsing.
I do have tests, but didn't see a standard way to trigger tests for utility functions like this.
Thanks!
-Erich