To create inline thumbnails locally, the previous version of the photo uploader
used base64 representations of the local files to be uploaded. While this is
effective, it is a little wasteful. When uploading several photos at once, this
could even lead to the page becoming less responsive.
This commit changes the process such that the photos are actually resized on a
canvas, only using the local original as a buffer. Hence, only the resized
photo is retained in memory.
