STORM-295. Add storm configuration to define JAVA_HOME

Here is a patch that adds support for JAVA_HOME. The patch does the following:
1. New file conf/storm-env.sh is added to setup environment. This is where JAVA_HOME is set.
2. I moved storm python script to storm.py. A new shell script storm sets up the environment variables and launches storm.py. 
3. Storm.py now uses java path derived from JAVA_HOME or uses java from PATH if JAVA_HOME is not set.