[test] AbstractService: Test for stateLog access as normal user

This test currently fails and therefore exposes a bug in the access
control logic of the AbstractService.
[Assets] Add 'dave' account, a conference owner
[test] AbstractService: Test for stateLog access as conf admin

User dave is neither abstract owner, nor site admin, but a
conference owner. As such he currently is denied to get the state
log, although he should be able to get it. Thi is issue  #186.
[service] Abstract:SL: use isOwner instead of owners.contains

This commit fixes the issue that abstract  owners (which are not
site admins) cannot access the abstract stateLog, because
owners.contains(account) did not find the account even though
it should have . isOwner converts the collection returned by JPA
into a scala Sequence and then uses contains. That works as
expected. See also issue #86.
[service] Abstract:SL: conference owners are also allowed

This closes issue #186
Merge pull request #196 from gicmo/stateLogFixes

Fix stateLog access for owner and conf. owner