[service] Abstract: apply() has now implicit request param

Fix all locations where request was not marked as implicit yet and
an AbstractService was created.
[service] Conferences: apply() has now implicit request param

Fix all calls without an implicit request in the package
controllers.api.Conferences()
[service] Figure: apply() has now implicit request param
[utils] DBUtils: functions now take an EntityManagerProvider

The EntityManagerProvider is the encapsulation object to get
the EntityManager. db{Query, Transaction} now take an
implict EntityManagerProvider to get the EntityManager from.
Change all Service classes + PermissionBase to provide that
implicit parameters. Fix tests as well.
This is the first major step to recycle EntityManagers.
Cleanup some imports
[utils] DBUtils: Don't close the EntityManager

Since we want to recycle EntityManager we must not close it.
[utils] Requests* are now EMPs and carry an EntityManager

We create an EntityManager in both, the AccountAwareAction and
the AuthenticatedAction and have the corresponding requests
carry them around. After we invoke the action's block the
EntityMangers are closed again. This is the next major step to
recycle EntityManagers.
[utils] DBUtils: new EntityManagerProvider.fromRequest()

Helper method to obtain an EntityManagerProvider from a request.
If the current request is indeed an EMP just return ist, otherwise
create a EMP from the DefaultPersistenceUnit.
[service] PermissionBase inc. valide() into setPermissions()

Inside setPermissions() we are already in an open transaction. If
we call validate() from within that transaction we will try to create
another one. This is unnecessary, but will also stop to work if we
re-use EntityManagers across dbTransactions.
[service] Abstract: Use EntityManger from request
[service] Conference: Use EntityManger from request
[service] Figure: Use EntityManger from request
[service] UserStore: move implicit EMP var into functions
[service] UserStore: findAccount: pass EMP implicitly
[utils] DBUtil: add an implicit from EM -> EMP

Needs to be explicitly imported since it is not in the companion
object of the EMP trait.
[utils] GCAAuth: use findAccount and reuse the EntityManager

This completes the recycling of Ems and therefore should fix the
issue #197.
[utils] DBUtil: add an implicit from Request[A] -> EMP
[service] {Figure, Abstract, Conf.} use new implicit req -> EMP
[controller] In all: bring implicit request -> EMP into scope

Preparation to convert services to take an implicit EMP instead of
the request.
[service] Abstract: Take implicit EMP instead of Request[A]

Clearer separation between service classes and web framework.