Jobs - Convert job_script's env_setup_commands to list.
Jobs - Allow destinations to declare arbitrary envirnoment variables.
See job_conf.xml.sample_advanced for examples.
Extend destination specific env options.
Add support sourcing files and executing arbitrary shell commands (see documented examples).
Merged in jmchilton/galaxy-central-fork-1 (pull request #378)

Allow specification of environment variables for job destinations