Integrate with city's tree disposal statistics

[joergreichert]

Current state: When trees are disposed it gets deleted from the database, and by this isn't visible in the app anymore (and by this also the waterings aren't visible anymore). Maybe It's replaced with a new tree at the very same place.

**Motivation:" There is new web site of the city that shows tree disposals along with the reason for the disposal: https://www.leipzig.de/umwelt-und-verkehr/umwelt-und-naturschutz/baeume-und-baumschutz/baumfaellungen/ Maybe we start not delete the tree in database but just mark it as disposed and link to the portal. So it's more informative for the users.

Future state: Disposed/replaced trees are shown in frontend and the reason for disposal / replacement are shown (retrieved / linked from source).