Site config host matching by regex, not ordered.
Use OrderedDict everywhere to maintain order of parsed config items.

And don't use where not necessary, in the config file spec modules.
Documented site config host matching.
Host matching doc update.
Merge branch 'master' into 212.site-host-pattern

Conflicts:
	lib/cylc/cfgspec/suite_spec.py
Merge pull request #638 from hjoliver/212.site-host-pattern

site config hostname pattern matching