Restore background mode when starting cylc gui.

This was removed by metomi/rose#370 with the thought that nohup would
normally return right away, but it looks like Python is still waiting
for the process to complete.
Merge pull request #373 from matthewrmshin/cylc-gui.bg

Restore background mode when starting cylc gui.
rose suite-log-view: fix job file name matching.

Increase dt threshold for matching file names, because it appears to be
taking longer between a task submit is reported in the Cylc suite log
and Cylc creating the job script.
Merge pull request #374 from matthewrmshin/log-job-filename-threshold

rose suite-log-view: fix job file name matching.