[34] Texture Manager

- New class TextureManager which help with fast loading MapChunks
- New Project Settings dialog
- Remove unused heightmap image
- Show Menus on entering World
- Show Chunk lines is now switchable
- Fixed MapChunks memory leaks!
- Added Texture Scaling option into MapView_Settings, currently for all textures
- Added Recent Projects into StartUp widget
- Moved QDataStreams about MapHeader into mapheader.h