AppData validation tool

A upstream maintainers have contacted me about some kind of validation tool for AppData files. I’ve spent a couple of days creating and then packaging appdata-tools which includes the appdata-validate command. This returns non-zero if there are any syntax or style issues with the AppData file.

I’d appreciate it if a few people could try it out before I start running it in the compose tool. There are already a few failures with the new builds in Fedora 20 Alpha RC3. If you’d rather install a package, I’ve just built it for rawhide, F20 and F19.

Comments and suggestions welcome.