* Fixed issue #3069 by adding in_channels

* Registerd group_conv2d_nchw as topi compute

* Improved by checking tag value

* Removed group_conv2d_nchw topi registration

* Added test for relay group_conv2d_nchw

* Added assertions to forbid small group size

* Removed hard-coded oc_block_factor

* Added explanatory comments to group_conv2d_nchw_cuda

* Updated group_conv2d_nchw_cuda schedule

Removed 'direct' CUDA tests

* Reverted an accidental change in a conv2d test

* Fixed indentation problems

* Fixed a mis-commented line

* Reverted change in group_conv2d_nchw tag

* Removed commented int8 group_conv2d test

* Fixed group size assertions in group_conv2d_nchw_cuda