Added NetworkIdentity Spawn Methods & Tests

[realQuartzi]

I have absolutely no clue why I felt like doing this <3

Adds the option to use NetworkIdentities to spawn Objects instead of the Object itself... sometimes saving a nasty GetComponent<> call.

SpawnObject(NetworkIdentity identity, NetworkConnection ownerConnection)

Spawn(NetworkIdentity identity, NetworkConnection ownerConnection = null)
Spawn(NetworkIdentity spawnIdentity, GameObject ownerPlayer)
Spawn(NetworkIdentity spawnIdentity, NetworkIdentity ownerIdentity)
Spawn(NetworkIdentity identity, Guid assetId, NetworkConnection ownerConnection = null)

No other functions modified, only new ones added... possibly some obsolete but I guess nice to have.
Hope none of the comments are wrong

Attempted to add Tests with the new Spawn Methods... these are possibly obsolete D:

ServerMode_IsFlags_Identity_Test()
HostMode_IsFlags_Identity_Test()
SpawnNetworkPrefab(GameObject prefab)

As well as fixed on minor issue with a already existing Test method which was using the wrong variable :)

Shutdown_DisablesAllSpawnedPrefabs()

And all tests still work just fine :D

[miwarnec]

@realQuartzi nice work.
shouldn't the Spawn(GameObject) methods then simply reuse Spawn(NetworkIdentity)?
it's the same code, right?

[realQuartzi]

@vis2k I guess one can do that yea... in reality I guess we are just doing one extra call to save an early GetComponent<>
I'll look into that when I get home 👍

[realQuartzi]

@vis2k I made some adjustments.
All the GameObject Spawns now use the NetworkIdentity SpawnObject method

I also added extra checks for the GameObject related methods to return the object name in an error log.
I have additionally moved the identity check to the top of SpawnObject as it is the first thing to look for now. Doing that skips the whole step of adding separate error checks in all the Spawn methods themselves as SpawnObject would take care of that.

It might be a little different than what you asked for but this might be better... at least in my thinking, it was.

[realQuartzi]

I hope this is okay. Got very confused midway. o.o
Should be up to date with the latest master branch.