Allow the cat-log command to print remote logs.

Addresses #709
cylc performance boosting: reduce bottlenecks
cylc performance boost: implement feedback
cylc performance boosting: tidy and speed up decorator
cylc performance boosting: GUI backwards compatibility
cylc/cylc#766: implement job filtering
Simplify job poll

The status of job is:
* submitted: job in queueing system, has no status file.
* submission failed: job not in queueing system, has no status file.
* running: job in queueing system, has status file.
* succeeded/failed: job not in queueing system, has status file.
cylc get-job-status: improve test stability

Improve loadleveler tests stability.
Merge branch 'master' into cylc-daemon-performance-rebase
Merge branch 'master' into cylc-daemon-performance-rebase
cylc/cylc#766: improve style
Merge branch 'master' into 766.job-submit-stderr-filtering
Merge branch 'master' into cylc-daemon-performance-rebase
Merge branch 'master' into improve-job-poll
Simplify job poll: remove redundant logic
Merge branch 'improve-job-poll' of https://github.com/matthewrmshin/cylc into improve-job-poll
Merge branch 'master' into improve-job-poll
Remove any old job status file on job submission

And improve stability of get-job-status loadleveler tests.
Merge pull request #808 from matthewrmshin/improve-job-poll

Simplify job poll
Merge pull request #805 from benfitzpatrick/cylc-daemon-performance

cylc daemon performance boosting