[INTERNAL] sap.ui.layout.Grid - Correct context is now returned from setters
[INTERNAL] sap.ui.layout.Grid - Correct context is now returned from setters

- All setters return correct context
- Global qunit test is added with gerrit change 1897995

Change-Id: I382443293306ec6b11203a6acc08fbf147e2d94f

olirogers/openui5,cschuff/openui5,nzamani/openui5,cschuff/openui5,SAP/openui5,olirogers/openui5,SQCLabs/openui5,SQCLabs/openui5,nzamani/openui5,olirogers/openui5,SQCLabs/openui5,cschuff/openui5,SAP/openui5,nzamani/openui5,SAP/openui5,SAP/openui5