Convert the whole MobileNet-v1 family

[psyhtest]

With #14, we've successfully converted MobileNet-v1-1.0-224 used for MLPerf Inference v0.5.

It should be pretty straightforward to convert the other MobileNet-v1-<multiplier>-224 models with the multipliers 0.75, 0.5 and 0.25.

It may be less straightforward to converted the other MobileNet-v1-<multiplier>-<resolution> with the resolutions 192, 160 and 128 because the resolution of 224 may be hardcoded in the program. If one exposes it via a command line flag (e.g. --input_resolution), it can be used in conjunction with the environment variables defined by the CK package variations for this family.