Annotate jpg images as well and notification about annotations

[kadarpik]

Current version installs well, there was little trouble with apache reverse proxy, just made typo, but tcpdump inside container helped.

I propose to expand the same concept into jpg files as well,

I propose an automated comment/another remark to file if someone has annotated the file, may be a tag after the annotation. May be I am blind too, I have just installed the app.

No need to overwrite an existing .pdf, it is not wise idea to destroy originals, but save as in adittion to download would be helpful - allows to share links for example.