Extending input_example() to take max batch and dimension arguments
This is to implement https://jirasw.nvidia.com/browse/JARS-1682.
It is important to provide user ability to generate input example of particular dimensions - as certain networks would reconfigure themselves according to input dimensions - thus export needs to be performed with real life size example.
Signed-off-by: Boris Fomitchev <bfomitchev@nvidia.com>