Statistics

Closes #33 (closed)

Significant notes

1. Added a new DTO class ReportCriteria holding a topic title and two time constraints.
2. Because the needs of the statistics page are too specific, I had to add two DTO classes TopReport and TopUser.
3. There is a way to select topics based on their title, as this is a unique index. So I have added a method to the TopicGateway that retrieves a list of all topic titles. @maderp this could be interesting for your moving reports.
4. Tests are completely missing, I know. Will come later. Prefer to have something working :)
5. It was necessary to adjust the DB views a bit and add yet another. Therefore the script is updated. This should however not affect anyone of you.
6. We should discuss about using OffsetDateTime by default as this is compatible with Postgres JDBC.
7. There is a nice way for SQL statements including filtering propsed by @mexis
8. Finally, this MR shows that @ViewScoped and PrettyFaces work perfectly well together.

Preview

In order to give feedback on the GUI without having to checkout the branch and starting the server, below a screenshot of the current state of this page:

Template Improvement

1. Most importantly for you: Dialogs!! Simply define them (arbitrarily many) with class dialog in a new area dialogs as shown in $6.
2. Aligned template with prototype from requirements.
3. Fixed profile menu. Logout is still to do.
4. Added search bar to top.
5. Implemented language change.

See the screenshot above for an impression.