change landuse=grass to landuse=meadow

[Masch]

Though I have used the tag landuse=grass while mapping I discovered yesterday that the correct tag for areas with grass is landuse=meadow. There is no landuse=grass described in the Wiki - except a proposal that was started yesterday.
I think the preset should be changed and a style should be added.

[ce]

Grass can be interpreted as "User Defined", so it's a valid value. According to tagwatch, we have lots of landuse=grass in the database. What about adding meadow and leaving grass besides it?

​http://tagwatch.stoecker.eu/Europe/En/tags.html

[ce]

Both meadow and grass already are in the presets.