Harmonize class/label information

[bwsw]

Currently, there are multiple ways to define classes and their labels and two ways to process that information. It looks like the state is not in sync, which can lead to unexpected and tricky results. We need to implement a single source of truth and prevent situations that can lead to unexpected results.

Our methods must allow setting:

• a class range without labels but with confidence constraints (leads to labels in class_0 format);
• a label list defined with a file with confidence constraints (leads to the contiguous class range);
• specific "label/class" pairs with confidence constraints and additional filtering options.

Our infrastructure, not nvinfer infrastructure, must handle all methods. Default processing must be implemented with our infrastructure, not nvinfer infrastructure.