Allow attaching multiple photos to a log

[mstenta]

In the app it appears to be possible to select/take multiple photos - but only the first one is uploaded to farmOS.

The photo capture/selection process seems to be inconsistent, too - but maybe that should be a separate issue. Using "Take picture", you can take a picture, and then take a second one. Neither of them are displayed in the app, and only the first is uploaded to farmOS. Using "Select photo from file", you can select multiple files, and they are all displayed in the app in sequence, but only the first is uploaded.

We should also add a way of removing photos that have been added, in case one was a mistake (otherwise you have to delete the whole log and start over).

[mstenta]

(Transferring all issues from old repository. See #92)

[mstenta]

I think this is no longer an issue. I just tested multiple photos and it worked. There are other open issues related to image UX, but this one is fixed.