improve natural=tree preset

adds field type (broad_leaved, conifer, palm)

See:
https://wiki.openstreetmap.org/wiki/Tree
http://taginfo.openstreetmap.org/tags/natural=tree#combinations
Follow existing convention for "Type" fields
Add footway=sidewalk preset
layer pane now matches help pane
Fix background pane tooltips
More area categories (fixes #1945)
Use warehouse icon
Update translations
add preset for amenity=shelter

http://taginfo.openstreetmap.org/tags/amenity=shelter#overview
http://wiki.openstreetmap.org/wiki/Tag%3Aamenity%3Dshelter