Removed the special 'sequential' task type.
Reimplemented sequential tasks with inter-cycle triggers.
(Re)Documented sequential tasks.
Fixed some test suites.
Fixed a typo.
Minor coding efficiency improvements (credit M.Shin).
Fixed some CUG typos.
Made unregister remove passphrase and suite.rc.processed.
Merge pull request #847 from hjoliver/fixed-some-cug-typos

Fixed some CUG typos.
Space after list-comma.
Extend registration test.
Corrected new obsoletion version numbers.
Merge pull request #849 from hjoliver/unreg-remove-passphrase

Made unregister remove passphrase and suite.rc.processed.
Corrected ready-to-spawn state list.
Sensible validation error for sequential async tasks.
Merge pull request #826 from hjoliver/810-remove-sequential-tasks

Removed the special 'sequential' task type.
Removed two accidentally-committed suite passphrases.