GitLab

* [Sparse] Add sparse matrix C++ implementation

* Add documentation

* Update

* Minor fix

* Move Python code to dgl/mock_sparse2

* Move headers to include

* lint

* Update

* Add dgl_sparse directory

* Move src code to dgl_sparse

* Add __init__.py in tests to avoid naming conflict

* Add dgl sparse so in Jenkinsfile

* Complete docstring & SparseMatrix basic op

* lint

* Disable win tests