Launch worker per environment settings

[anfeng]

To launch storm workers in a cloud environment, we need to handle some minor issues:

• worker's logs have to be located in certain directory (instead of current working directory)
• logback configuration file is located in a distributed file system directory (instead of current working directory)
• JAVA_HOME needs to respected if it's specified in an environment

This pull request makes the following challenges to supervisor's logic to launch workers:

• If JAVA_HOME is specified in an environment, we will use <JAVA_HOME>/bin/java
• If "worker.logdir" is specified in supervisor's command (-Dworker.logdir=xxxx), worker logs will be stored in that directory
• worker's logback configuration file will be identical to supervisor's logback configuration.

[d2r]

Would it be good to use the File/separator instead of "/" while we are changing this?