By integrating with dynmap the plugin can show the area of the generation task for each world via an area marker and
triggers the rendering of tiles for generated chunks.
- added config parameter to define the number of chunks that should be generated per step
- probably fixed#3 by processing or canceling pending chunks before the world is saved
- Added interface GenerationTask
- added method to GenerationManager that creates a task depending on the server type
- added generation task for paper and spigot (to profit from async chunk loading)