Updated the change log for 5.4.0
Update graph string interp doc.
Updated User Guide on inter-cycle triggers at start-up.
Updated User Guide on warm starts.
Load the Jinja2 'do' expression-statement extension.
Graph view option to crop runahead tasks.
Added tests for jinja2 do extension and command line set.
Check default runahead limit being enforced.
Add special task testing for sequential and one-off tasks.
Graph view: also crop tasks held beyond final cycle time.
Test (not just load) jinja2 do extension.
Merge remote branch 'upstream/master' into expand-battery-8
Merge pull request #762 from hjoliver/jinja2-do-extension

Load the Jinja2 'do' expression-statement extension.
Merge remote branch 'upstream/master' into expand-battery-8
Added testing for special tasks.
Tidy.
Merge branch 'master' into release-prep-5.4
Documented triggering off tasks in other suites (by polling).

Also updated the User Guide for the recent REGDB changes.
Updated the change log for 5.4.0.
gcylc back compat for new err log functionality.