1.2.1 release notes (apache#11478)

* Release notes 1.2.1

* Fix RELEASE Notes

* Remove line

* Fix within namescope issue

* Remove bullet

* Change the tutorial link

* Fix gluon without namescope line

* Fix gluon book link

* Add info to NEWS

* Add Saving and Loading Gluon models tutorial line

* Add NEWS.md

* Fix save_parameters and load_parameters

* Fix NEWS

* Add NEWS.md

* Change save_params/load_params to save_params

* Semantic versioning line

Fix discard_stderr (apache#11309)

add apache-release as parent to pom file (apache#10941)

add apache-release as parent to pom file (apache#10941)

fix kvstore rowsparse pull (apache#10777)

* fix kvstore rowsparse pull

* Trigger CI

* fix compilation error

Add known issue to README (apache#10700)

* Add known issue to README

* Add scala example to known issue

[MXNET-293] Navigation updates (apache#10449)

* Changes for SIM AWSDBUX-19875
1. Add ONNX to Docs
2. Move Github to Community
3. ename Gluon Model Zoo to Model Zoo

* Removing Gluon from the Navbar and correcting the link for ONNX

* Re-ordering the elements in the Navbar for SIM AWSDBUX-19875

* In the navbar, changing the Github URL to to apache/incubator-mxnet

* Removing gluon and github from navbar.js

* Adding Gluon back to the Navbar

[MXNET-293] Navigation updates (apache#10449)

* Changes for SIM AWSDBUX-19875
1. Add ONNX to Docs
2. Move Github to Community
3. ename Gluon Model Zoo to Model Zoo

* Removing Gluon from the Navbar and correcting the link for ONNX

* Re-ordering the elements in the Navbar for SIM AWSDBUX-19875

* In the navbar, changing the Github URL to to apache/incubator-mxnet

* Removing gluon and github from navbar.js

* Adding Gluon back to the Navbar

[MXNET-185] Improved error message (apache#10424)

* Improved error message

* fix pylint errors

* addressed PR comments

* fixed lint issues

* lint error fix

* append  warning message

* lint errors

* removed redundant message

* fixed warning

* Update block.py

update navbar model zoo link (apache#9749)

* update navbar model zoo link

* update