Moved some MXNet-related code to CNNArch2MXNet and CNNArch2Gluon

2 jobs for develop in 5 minutes and 46 seconds (queued for 2 seconds)
Status Name Job ID Coverage
  Windows
passed masterJobWindows #431262
Windows10

00:04:01

 
  Linux
passed BranchJobLinux #431263

00:01:45