Add rows and columns to plot

Post routes create needed relationships when creating new entries.
The associated entires are deleted on deleting an entry (e.g. deleting a project
leads to deleting all visualizations and plots belonging to this project.

Change response on delete routes.

Add UML class and use-case diagram (StarUML application).
Add admin user from config if no admin user found.

User passwords are stored with bcrypt hash & salt.
The authentication token is stored in the 'x-access-token' header.

For tests open mongodb port and access directly (without docker)