Partial impl of LocalActorRefProvicerSpec (#59)

Still left to implement (and functionality?) for invalid actor names.

Changes:

- Changed behavior of ActorOf so it doesn't copy Props when no Dispatcher or
Mailbox is given in the Deploy object, or when there is no Deploy in
configuration.

- In Depliy, force Scope, Dispatcher and Mailbox to be set to NoScopeGiven,
NoDispatcherGiven and NoMailboxGiven in case of null values to
constructor.

- Introduced new exception type InvalidActorNameException.

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