XWikiSyntax* translations are very hard to maintain

There is a lot of things to understand to properly translate it and it's very easy to break things (and there is many mistakes in the current translations).
Most of the translations are also totally out of date because it's not easy to see that there is new things to translate.

It should be refactored to be based on key=value translations resources:

• translator just translate plain text and it's a lot harder to make mistakes
• it removes a lot of copy pastes between syntaxes
• no missing information anymore, anything new will be in default language until it's translated and it appear as empty new translation on http://l10n.xwiki.org