LocalActorRefProvicerSpec + bug fixes. Fixes #59

- 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. This prevents creating a new instances of Props when it
  would be equivalent to the old.

- In Deploy, force Scope, Dispatcher and Mailbox to be set to NoScopeGiven,
  NoDispatcherGiven and NoMailboxGiven in case of null values to
  constructor, so we can always compare with only the null object.

- Changes to Actor name regex because of differences between CLR and JVM:
  - a-zA-Z0-9 instead of \w (latter includes non-Latin characters)
  - added CultureInvariant option
  - added ^$ because regex to match whole string (Scala does this when
    matching regexes using pattern matching)

- Changed exception type and messages for null/empty Actor names.
PR fixes for issue #59
Added explanation of WhenAll/ContinueWith trick in unit test
Merge pull request #517 from cpx/dev

LocalActorRefProvicerSpec + bug fixes. Fixes #59