-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

clang format updates

self-review cleanups

cpplint fix

review updates

ci fixes

support for 1 specific dimension to be None, added validator

fix various CI complains

another round of CI fixes

ci

refactor parts of the code

code refactor

ci fix

comments added, fix bugs

address review comments

address review comments

review cmts

added simple perf test script

update pad code

perf imprv

fix some ci failures

more ci fixes

more ci fails

yet another ci fail

more ci stuff

still ci

more ci

more ci

more ci

fix clang

pybind fix

Signed-off-by: leonwanghui <leon.wanghui@huawei.com>