* make the standard queries "single method interfaces" that may be implemented
by a query journal plugin
* remove hints (major problems with varargs anyway), the hints for standard
queries should be given in configuration instead, e.g. refresh-interval
Existing tests covering stashin in PersistentActor moved to separate
test class.
New async write journal for tests SteppingInmemJournal allows to
control the async journal operations tightly from a test. Each journal
operation requires a token which the test then can wait for consumption of.