TerrainFactoryWithSideWalls needs consistent naming

[apavani]

• Unity version: Unity 2017.2.0f3
• Mapbox SDK version: 1.3
• The platform you're building to: iOS
• A description of what you're trying to do: Create Terrain Factory with side walls

The issue is that there has been some naming discrepancy with the TerrainFactoryWithSideWalls that needs to be consistent with the .cs filename. Because the filename doesn't match with Class name it causes the Scriptable Object to become corrupt after it has been generated.

Proposed Solution: Rename the file TerrainFactoryWithSideWalls.cs to match with the class name i.e. TerrainWithSideWallsFactory