+per #15279 FSM for PersistentActor

Located in akka-persistence because persistence is experimental and probably should not be used in akka-actor
I've changed 
```java
val persistentId = randomId
```
to 
```java
val persistenceId = name
```
when `name` variable comes from `PersistenceSpec`. I've changed `PersistentFSMActorSpec`:
```java
class PersistentFSMActorSpec extends AkkaSpec with PersistenceSpec with ImplicitSender {..
```