Remove XML mappaint support

[Don-vip]

We have today 81 styles listed on styles.

Only 7 of them are still in XML format. I propose to rewrite them in MapCSS and drop support for old XML styles:

1. ​https://github.com/avar/osmis-josm-style/blob/master/elemstyles_is.xml ==> to rewrite
2. ​http://www.freietonne.de/ft_icons/josm/FreieTonne_rules_presets_zip.php ==> To drop (presets already dropped because authors don't respond to fix errors)
3. Styles/FrenchEPCI ==> to rewrite
4. Styles/LegacyStandard ==> to remove from list
5. Styles/Lit ==> to rewrite
6. Styles/MaxspeedIcons ==> to drop (integrated in core)
7. Styles/Traffic_signs ==> to rewrite

I don't remember how we switched from XML to MapCSS: is there a transformation script somewhere? All styles are quite small except traffic signs...