Namespace definition ordering for gcylc dot and tree views.

Temporarily switched off by hardwired flag - pending testing, and
click-toggle for dot-view.
Switch off experimental definition ordering.
Removed temporary gcylc definition order flag.
Merge branch 'master' into 160-gcylc-definition-ordering
Defn order default for tree view.
Toggle definition order for dot view.
Merge branch 'master' into 160-gcylc-definition-ordering

Conflicts:
	lib/cylc/scheduler.py
	lib/cylc/state_summary.py
Merge branch 'master' into 160-gcylc-definition-ordering
Switch for gcylc definition order.
Added a gcylc.rc reference to the user guide.
Merge branch 'master' into 160-gcylc-definition-ordering
Default to definition order on.
Merge pull request #893 from hjoliver/160-gcylc-definition-ordering

Namespace definition ordering for gcylc dot and tree views.