[segmentation] Add drishtigs1 database

...masks/Drishti-GS1_files/Training/Images/drishtiGS_092.png

...masks/Drishti-GS1_files/Training/Images/drishtiGS_094.png

...masks/Drishti-GS1_files/Training/Images/drishtiGS_098.png

...masks/Drishti-GS1_files/Training/Images/drishtiGS_101.png

...t/libs/segmentation/config/data/drishtigs1/optic-cup.json

.../libs/segmentation/config/data/drishtigs1/optic-disc.json

...libs/segmentation/config/data/drishtigs1/optic_cup_all.py

...libs/segmentation/config/data/drishtigs1/optic_cup_any.py

...ibs/segmentation/config/data/drishtigs1/optic_disc_all.py

...ibs/segmentation/config/data/drishtigs1/optic_disc_any.py

...ams/models/histograms_lwnet_drishtigs1_optic_cup_all.json

...tograms/raw_data/histograms_drishtigs1_optic_cup_all.json

src/mednet/libs/segmentation/tests/test_drishtigs1.py