Adding water park styles and icon

This change is to fix issue #370. It adds the necessary styles,
icon, and SQL queries to properly render water parks.

It also fixes the rendering of playgrounds in the process. (Since
playgrounds have an icon, they also need a text offset.)
Merge branch 'master' of https://github.com/kaldari/openstreetmap-carto

Conflicts:
	amenity-points.mss