Make public boards more visible
Advertising devices that can be used by anybody are tagged with "access=yes" (cf. wiki)
With this merge request:
- public boards have green markers on the map
- multiple values for "message" is supported (typical example: "message=opinion;non_profit")
- support deprecated value "opinions", which is now handled like "opinion"
These changes make it easier to distinguish between commercial advertising boards and boards available to citizens. You can see the differences in Montrouge for example.