Add CODEOWNERS file and merge request templates for gitlab

Add codeowners and merge request templates to gitlab. Related to #209 (closed)

.gitlab/merge_request_templates/Bug.md

+# What does this mr do?
+<!--Describe in short what the bug was.-->
+
+# Actions taken to fix bug
+
+# Does this MR meet the acceptance criteria?
+* [ ] A test was created to test the bug.
+* [ ] I have updated the documentation accordingly.
+* [ ] I adhere to the style guide.