Add new change state "deferred".

Support for new change state "deferred" to be able to discern
"really dead" from "postponed" changes. This is equal to "abandoned"
for all practical purposes except presentation and filtering. State
transitions are possible between "review in progress", "abandoned"
and "deferred". And menu bar has new "All/deferred" and "My/Deferred
Changes" default filters.

Task-number: QTQAINFRA-598
Change-Id: Ib1801f35eabf6b3b32bf41b0f3b5b496fbcda72a
Reviewed-by: Ismo Haataja <ismo.haataja@digia.com>