add introduction lecture for 2020

Author: cstenkamp

.gitignore

@@ -5,3 +5,4 @@ __pycache__/
 usernamepw.py
 cache*.json
 id.py
+.nbgrader.log

jupyter_notebook_config.py

@@ -1,5 +1,5 @@
 # Set options for solutions.
 c.JupyterLabRmotrSolutions.is_enabled = True
-c.JupyterLabRmotrSolutions.role = "student"
+c.JupyterLabRmotrSolutions.role = "student" #student, teacher
 # Enable compression, which makes sense on binder.
 c.NotebookApp.websocket_compression_options = {}