Need more error checking of analysis task output

[stevekm]

• [x] check qacct for compute jobs to verify exit status and check for jobs that finished with errors
• [x] if its a qsub job, check that the job completed successfully
• [x] check that expected task input files exist
• [x] include in config per analysis step expected output file(s), and check that files exist upon completion of analysis step
• [x] raise exceptions inside analysis tasks if task completion validations do not pass
• [x] have separate email for errors and successful results, email only dev's & users in case of an error
• [x] custom actions when custom exceptions are raised