some classes are missing from the autogenerated API docs

[wyli]

Describe the bug
the autogenerated API docs don't show all the classes defined in monai codebase

To Reproduce
visit https://monai.readthedocs.io/en/latest/apidocs/monai.transforms.html#monai-transforms-package

Expected behavior
list all class interfaces such as AddChannel defined here:
https://github.com/Project-MONAI/MONAI/blob/master/monai/transforms/transforms.py#L30

[Nic-Ma]

And I found the doc-string format is changed in web page:

Expected to be:

[wyli]

@Nic-Ma I think that is a separate docstring style issue

[wyli]

fixed by #158

all docstrings need to be checked to address the formatting style issue.