Previously @mquandalle took care of packaging Wekan for Sandstorm, so
he was listed as the sole author of the SPK. Since I'm now taking over
packaging, this commit moves @mquandalle into the `upstreamAuthor`
slot and adds me as the SPK author by using my email address for
`contactEmail` and adding a pgp-signed statement that I am now an author.
It also adds my public key to the `keyring` file.
It seems that the total size of the sandstorm package manifest can't
exceed a certain size. Putting a small image works until I figure out
what the issue is.
We still miss some branding stuff, such as screenshots, icons, and a
description.
This commit also hides an option related to user permissions managment
in the sandstorm package.
