ISIS-528: handle domain objects new'ed up rather than through newTransientInstance()
ISIS-520: fixing regression (infinite loop if run under Tomcat).
ISIS-529: hidden versions of setting services.
ISIS-530: upgrades to wicket 6.10.0
ISIS-531: reinstating metamodel "API" classes.
ISIS-533: keep flushing until no more commands to flush
ISIS-535: application-specific logging example

executing the ToDoItem#updateCost action will log to Stderr (debug level)
ISIS-536: thread local as a means of temporarily disabling concurrency checking.
ISIS-478,ISIS-503: various fixes.

ISIS_478, for conditional choices, for EntitySelect:
* clear link now should work
* if no choices/autocomplete then doesn't NPE (BankMandates#newBankMandate)
* removed ID_ENTITY_TITLE_NULL label, since never visible
* sets up a placeholder text
for conditional choices, for ValueSelect:
* correctly initializes second dropdown based

ISIS-503, for contributee actions/associations, calculate identifier
* was causing stack trace when go back to list, caused by call to getIdentifier() incorrectly returning the wrong value for a contributed association.
ISIS-74: removed BoundedFacet

instead, @Bounded implies a ChoicesFacet on the type, from which are derived
PropertyChoicesFacet or ActionParameterChoicesFacet (same as handling of
enums).

Also removed use of deprecated Filter interface in ToDoItem, using guava
Predicate instead.
ISIS-473: actions now need to be explicitly annotated as @Bookmarkable

(they must also have safe semantics, as previously).