addons: fix pluginsource.xsd
addons: remove unused "content" element from pluginsource.xsd
addons: remove "wingl" as a possible platform value from metadata.xsd
addons: fix repository.xsd
addons: add "cachepersistence" attribute to scraper.xsd
addons: add service.xsd
addons: add "res" element to skin.xsd
addons: remove unused "defaultthemename" attribute from skin.xsd
addons: rename "defaultresolutionwide" attribute to "defaultwideresolution" in skin.xsd
addons: "defaultresolution" attribute is optional in skin.xsd
Merge pull request #5996 from Montellese/fix_addon_xsd

addons: fix <extension> XSDs