change ImagefolderDV2 name

change ds.transforms.vision to ds.vision

change batch api to match map api more closely

compose op changes

test_pylint

remove compose op from vision, move to transform module, refactor map and batch to use column_order

-replace switch'case by indexing

- Add test case
- Add constructors
- Add getItem string

- Fix bugs
- Add more tests

- Tensor iterator
- asNumpy
- TextFileDataset

- Tensor(Numpy)

- Super > 2D
- Add more test cases for GeneratorDataset

- Change StartAddr to GetBuffer and GetMutableNuffer

- Raise an error if batch is used with strings

Clean-up work