Memory Optimization, better progress display, TF 1.15.x Support & Dataset regeneration

Added mini-mask support that help reducing memory usage.
Optimized few processing (mask drawing, post-processing...).
Improved progress display using progress bar during inference, masks fusion & filtering.
Added TF 1.15.x support (GPU is usable through Google Colab Inference Tool).
Fixed few bugs (post-processing filtering, mask drawing method...).
Added Dataset regeneration mode to dataset generator (may depend on your libraries versions).