Basic charge report

[JeremyMahieu]

This is a work in progress!!

Just wanted some opinions, I have a working charge report. I did change the models a bit so the start and stop tags are objects instead of IDs, however it doesn't change the database. I didn't test it though, so maybe it gives some runtime exceptions.

This is related to issue #56

Still needs to be done:

• [x] CSV and XLSX exports
• [ ] detail view when clicking a tagname.
• [ ] One datetime picker that selects a range instead of two datetime pickers
• [ ] Have sensible date fromatting (not MM-DD-YYYY) perferably system default
• [ ] Localization

[dallmann-consulting]

I'm on vacation this week and will check next week.

[JeremyMahieu]

Did some more work