tests-extra: extended events/soa tests with zone restarts.
persistent events: Initial implementation
namedb: fixed leak, lmdb iteration

Conflicts:
	src/common/namedb/namedb_lmdb.c
	src/common/namedb/namedb_trie.c
persistent events: reusing the events + db sweep
tests-extra: Extened events test with restart/reload combo
persisten events: Added files with timer db impl.
namedb-api: Changed insert behaviour from append to replace.
persistent-events: Moved timer db opening from main to conf.c
remote: Do not write timers after event planning.
server: Removed some blasts from the past
persistent-events: Write timers after reload

 - needed because of master -> slave role switch
lmbd namedb: ifdef fixed
tests-extra: tweaked the event timers test
persistent-events: Doxygen for timer API
persistent-events: fix build without lmbd
persistent-event: Do not query zonedb for each event.
tests-extra: Extend expire timer in event test.
namedb: symbol prefixes, copyrights, trailing white spaces
timers: fix API change
persistent-events: review remarks.