* go through gcn, relgcn
* fix tagconv formula
* fix doc in sageconv
* fix sgconv doc
* replace hat with tilde
* more comments on gmmconv
* fix agnnconv chebconv doc
* modify nnconv doc
* remove &
* add nn conv examples
* Rebase master
* More merge conflicts
* check homo
* add back self loop for some convs, check homo in tranform
* add example for denseconv
* add example and doc for dotgat and cfconv
* check in-degree for graphconv
* add language fix
* gconv address all comments
* another round of change based on api template
* change agnn
* go through agnn, appnp, atomic, cf, cheb, dense, gat, sage modules
* finish pytorch part of nn conv
* mxnet graphconv done
* tensorflow graphconv works
* add new modules into doc
* add comments to not split code
* refine doc
* resr
* more comments
* more fix
* finish conv and dense conv part api
* pylint fix
* fix pylink
* fix pylint
* more fix
* fix
* fix test fail because zere in degree
* fix test fail
* sage is not update for mxnet tf
Co-authored-by: Ubuntu <ubuntu@ip-172-31-0-81.us-east-2.compute.internal>
Hongzhi (Steve), Chen