Adds support for high lod terrain in the map viewer, gltf mesh export, fixes mesh rendering bugs, and more.

See Nanoforge basics for a guide on how to use Nanoforge and it's features.
See Nanoforge xtbl editing for a guide on using Nanoforge to edit xtbls.
See Nanoforge texture editing for a guide on using Nanoforge to edit textures.

Changes
- High resolution terrain support in the map viewer.
- Added LOD slider to the mesh viewer.
- The mesh exporter now exports gltf files instead of obj files. Different lod levels are organized into their own subnodes and labelled.
- Removed the file cache.
- Nanoforge now limits the number of threads it uses to avoid lagging other apps. You can adjust the limit in `File > Settings`
- Added 'Tasks' button at the bottom left of the screen that shows all background tasks when clicked.
- Proper SRGB texture rendering. SRGB flag on pegs was previously ignored.
- Less useful texture info in the viewer is now placed in a "Additional info" section that's collapsed by default.
- Improved settings.xml regeneration / upgrades
- BUG: Fixed mesh rendering and export bugs like erroneous triangles and inside out meshes.
- BUG: Fixed slow & infinite texture searches in the mesh viewer. Searches can still fail, but they'll fail quickly.
- BUG: Fixed missing triangles in low lod terrain.
- BUG: Fixed a crash when minimizing Nanoforge while a mesh or map viewer is open.

See Nanoforge on Github for a list of changes made by previous releases and see the readme for more info about Nanoforge.

Important notes
- High lod terrain can use a lot of RAM while loading. You can decrease it by lowering your thread limit or disabling high lod terrain completely in `File > Settings`. You must restart Nanoforge for thread limit changes to go into effect.
- If you notice system wide visual or audio lag during map loading you should lower your thread limit or close other apps with high CPU usage.
- Disable high lod terrain for quicker map loading.
- Delete your 'Cache' folder if installing over older versions. The cache has been removed.
- Meshes now export as gltf, which doesn't use the same material model as RFG. In effect, most meshes look bad by default when imported into blender. Eventually an extension will be made to auto fix this. For now you need to manually make the following changes in the shader graph:
- Set the color space of the diffuse & specular textures to linear, and of the normal texture to SRGB.
- Map the color output of each texture to the following input nodes of the principled BDSF shader. Remove any intermediate nodes added by blender:
- Diffuse texture -> Base color
- Specular texture -> Specular
- Normal texture -> Normal

This file hasn't been reviewed yet. Tell us what you think!