Release 0.4.0

Biomemap generator 🏭

Abandon linked list structure of STPLayer. Add a separate master manager STPLayerManager.
Re-implement STPBiomeFactory with a better programmable interface, as well as concurrent heightmap generation and memory management.
Integrate demo biome generator into the generator pipeline.
Import settings from Biome.ini.
Biomemap can now be stored in STPChunk and loaded into OpenGL rendering buffer.

Add STPDiversityGenerator which contains some high-level helper functions for simple runtime complication.
Allow programmable heightmap generation, such that user can develop their biome-specific algorithms.
Allow runtime-compiled script for heightmap generator. Current heightmap generation pipeline will become deprecated and change to programmable pipeline in future release.

Also note that all heightmap generator parameters like octave and persistence will be depreacted in future release.

Separate chunk management engine and heightfield generator, so creating renderer won't lead to a chained creation of STPChunkManager, STPChunkProvider and STPHeightfieldGenerator. Instead, individual parts need to be created by user and linked to the dependee program by reference. This gives user better controls on whether they want to share it with other pipeline, for example.
Add a high-level management unit STPWorldManager in case developer doesn't need such control mentioned above and wish to init the generator with ease.

For more technical details please refer to the pull request page 👉🏼 #19.