Wox Plugin Management upgrade

[lances101]

Wox is getting bigger and bigger so it's hard to control the plugins that users submit to Wox's plugin management system. In order to keep Wox users safe and make the plugin management system better we need a couple of changes on the web:

• Obligatory GitHub repo link for submitted plugins (special cases may apply, but still)
• Every new build must be moderated and reviewed before being accepted
• Executable plugins must provide source code for executables.
• Handle plugin updating: update API

Users will still be able to install plugins without WPM by dragging .wox packages onto Wox, but the official plugin management system should be a safe haven.