new docs

...ns/aa_learners/autoaug.autoaugment_learners.AaLearner.rst

...s/aa_learners/autoaug.autoaugment_learners.EvoLearner.rst

...s/aa_learners/autoaug.autoaugment_learners.GruLearner.rst

...ns/aa_learners/autoaug.autoaugment_learners.RsLearner.rst

...s/aa_learners/autoaug.autoaugment_learners.UcbLearner.rst

docs/source/explanations/autoaugment_learners.rst

docs/source/howto/AaLearner.rst

docs/source/howto/AutoAugment.rst

docs/source/howto/howto_main.rst

docs/source/howto/installation.rst