Added serialization / deserialization

• Now we can define transformations in a python dictionary, json, yaml files and they will be deserialized and used in the code.
• Now we can define transformations in the code and serialize them in python dictionary, json and yaml files.

Jupyter notebook with an example

Special thanks to @creafz

Added new transformations

• Lambda
• GaussianBlur
• ChannelDropout
• CoarseDropout
• RandomSnow
• RandomRain
• RandomFog
• RandomSunFlare
• RandomShadow

Special thanks to @vfdev-5 @ternaus @BloodAxe @kirillbobyrev

Bugfixes and improvements

• Bugfix in ToGray
• Bugfix in ShiftScaleRotate
• Bugfix in GaussNoise
• Added fill_value parameter to CutOut
• SpeedUp in RandomBrightnessContrast

Special thanks to @qubvel @ternaus @albu @BloodAxe