* nms fixed for gpu, tested on cuda and opencl devices, ssd now can run fully on the gpu

* sort updated to use virtual thread

* typo fixed

* fix lint

* fix lint

* add support when batch_size > 1

* intel graphics conv2d bugs fixed for inception_v3

* intel conv2d api updated, nn input size 4 condition added

* review addressed

* move conv_tags to attributes

* opencl ctx fixed

* nms_ir index simplified

* add ssd ops to mxnet.py

* add ssd ops to mxnet.py

* add result check for multibox and nms unit tests

* add result check for multibox and nms unit tests

* address @kevinthesun's comments

* Disable cuda test for nms for now.

moving nnvm/testing/download.py to python/tvm/contrib/download.py to be used as a general TVM download utility