appdata: Improve appdata for AppStream 1.0

[sabriunal]

• Use appstreamcli to validate appdata
• Add the <developer><name> tag
• Mark the <developer_name> tag as deprecated
• Update bugtracker and translate URLs
• Add vcs-browser URL
• Mark release description as untranslatable
• Update broken homepage URL

[ghost]

@sonnyp Ready to be reviewed.

[sonnyp]

@sabriunal why dd you close this?

I hope you didn't take offense in https://github.com/workbenchdev/Biblioteca/pull/37 - that wasn't my intention and I appreciate your contributions. I just need time to go through them because I maintain a lot of different things.

[ghost]

I'm a bit touchy/irritable these days. I'll try to be more reasonable.