Release 0.8.1

Refactoring

Deprecate selective edge copy algorithm introduced in #17. Remove normalmap generation from heightfield generator pipeline. Remove normalmap from rendering buffer.

Now, heightfield rendering only contains a single channel of formatted heightmap of unsigned int, i.e., R16.

Normal calculation in geometry shader in SuperDemo+.
Change STPChunkManager and STPHeightfieldGenerator as well as shaders to address the changes.
Move Strength from STPHeightfieldSetting to STPMeshSetting since normalmap will no longer be generated using our engine. Now mesh surface normal calculation can be done in either geometry shader or fragment shader.
Remove prototype testing for Sobel filter from SuperTest+ since normalmap generation is no longer needed.

Move the following CUDA global functions to a new file STPHeightfieldKernel, and use a host function wrapper to launch the device kernel. Note that all host function wrapper comes without the KERNEL suffix.
- From STPHeightfieldGenerator
  - curandInitKERNEL()
  - performErosionKERNEL() renamed to hydraulicErosionKERNEL()
  - generateRenderingBufferKERNEL() renamed to texture32Fto16KERNEL()
- From STPFreeSlipGenerator
  - initGlobalLocalIndexKERNEL()
Hence, all instances of global functions in the original classes mentioned above are removed. This greatly reduce the code complexity.
Relocate the following files from /GPGPU directory to /World/Chunk:
- STPHeightfieldGenerator
- STPDiversityGenerator
- All files under /FreeSlip
Rename the suffix of the following files from .cuh/.cu to .h/.cpp
- STPHeightfieldGenerator
- STPFreeSlipGenerator