[MagTek.iDynamo] Fix up native library slices

I think the downloaded zip contents changed at some point, but retained the same file name?  Not sure what happened, really.

The native library no longer contains an ARMv6 slice, so I removed that from the binding.
The native library now contains an ARMv7s slice, so I added that to the binding.

I also added a slice to support the simulator.  I guess it could be argued that this library is useless in the simulator, but I didn't like having the build warning.

The "ARMv7 support" section of the ReadMe is no longer applicable, so I removed it.