Feature implementation tracker: Template-based cluster executors

[gdevenyi]

Just putting this here to track the transition to template-based job submission and for testing/feedback

• [X] SGE - complete in sge_fixes
• [ ] torque/PBS
• [ ] slurm
• [x] LSF

[gdevenyi]

I have access to a PBS/Torque cluster, so I can conceivably test bpipe on that cluster and provide feedback

[ssadedin]

See https://github.com/ssadedin/bpipe/issues/168 for LSF implementation