Landscape GrassType does not have the option to exclude Decals

Landscape grass type lacks the option to disable decals from affecting it.

1. Open UE4
2. Use a simple LandscapeGrassType asset
3. Paint some of the grass type asset.
4. Add a Decal actor over some of the grasstype actors

Results: No option to disable landscape grasstype from receiving a decal

Expected: option to disable grasstype from receiving decals.