user interaction for Glossary

[kohlhase]

We will make the glossary public step by step in the next months. Thus more people will want to interact with it. We should give people the ability to

• get help on what they are seeing and how to interact with it (see add help text to glossary (and its items) #151)
• edit the sources, if they have sufficient permissions (see [Glossary] Add Edit Button  #10)
• create comments and issues (see #31 "issues/comments" dialog on glossary items #152)

[kohlhase]

Assigning to Mihnea for now.