There is no way to change the path to collection in the database, 
if collection is moved (e.g. disk with photos is mounted into different directory).

Reproducible: Always

Steps to Reproduce:
1. Add "Local Collection" to digiKam
2. Close digiKam
3. Rename the directory, where "Local collection" files are located
4. Start digiKam
5. Try to update the path to collection
Actual Results:  
In Settings -> Configure digiKam -> Collections
collections are listed with paths to them, 
but there no option to change the path.

Expected Results:  
In Settings -> Configure digiKam -> Collections
there should be an option to change the path to collection.