Add RandomApply, RandomChoice, RandomOrder transformations

[vfdev-5]

Some handful classes to randomly apply list of transformations:

1. Random apply: applies a list of transformation with a probability

RandomApply(
            [
                transforms.RandomRotation((-45, 45)),
                transforms.RandomHorizontalFlip(),
                transforms.RandomVerticalFlip(),
            ], proba=0.75
)

2. Random choice: choose randomly a single transformation from a list
3. Random order: apply transformations in a random order

[vfdev-5]

Any feedback on the PR is highly appreciated :)

[fmassa]

Looks useful, thanks!

I have a minor comment: for consistency with other transforms, might be better to rename proba with p. What do you think?

[vfdev-5]

@fmassa fixed