support uploading multiple files #83
Description
When selecting multiple images a dedicated dialog should be presented to the user. This dialog should be similar to the single-file-dialog, but additionally:
- have a toolbar button, to show a vertical, scrollable list of the selected files
- when uploading the captions, descriptions and tags are used for all files, but geo locations should stay individual
- the filename for each file is derived from the shared caption, adding a suffix (eg. numbering, 1-999)
- suffixed filenames for each file has to be checked individually for uniqueness and support a fallback variant (eg. 1-999 + a-z) otherwise display an error
Optional/nice to have:
- overriding the shared captions/descriptions/tags for individual files
- reviewing changes in a scrollable list with relevant info about the files, customized changed etc. before upload
- sanity checks: when the max distance of camera coordinates are over a certain threshold, show an info-box, to potentially adjust caption/categories