New augmentations

TemplateTransform. This transform allows the blending of an input image with specified templates. (#572 by @akarsakov )
PixelDistributionAdaptation. A new domain adaptation augmentation. It fits a simple transform on both the original and reference image, transforms the original image with transform trained on this image, and performs inverse transformation using transform fitted on the reference image. See the examples of this transform in the qudida repository. (#959 by @arsenyinfo)

Minor changes:

LongestMaxSize and SmallestMaxSize now can also accept a list of sizes as their max_size argument and the actual max_size value will be sampled randomly from this list. (#930 by @kmistry-wx )
A.Affine now accepts mask_interpolation as a parameter. (#975 by @dskkato )
A.RandomRain now alters brightness in HSV space instead of HLS space to prevent image corruption. (#990 by @ErlingLie)
Albumentations now raises ValueError if bbox_params is not specified and bbox transformation is called (#1013 by @VirajBagal)
CoarseDropout can now set the height and width of holes based on the fraction of original image height and width (#1014 by @VirajBagal )
ElasticTransform got performance optimizations. (#1004 by @b0nce)

Fixed a bug when CropNonEmptyMaskIfExists thrown an error when it was used with a keypoint even though keypoints were mentioned as a correct target. (#986 by @GalDude33 )
Fixed KeyError with RandomCropNearBBox when it received values with x_min <= 0 or y_min <= 0 (#993 by @Dipet )