[FEATURE]: Chaning of .obj/.ply files into .blend files

**Is your feature request related to a problem? Please describe.**
Loading `.obj` or `.ply` files takes forever, it would be much nicer if those can be loaded at the same speed as `.blend` files can be loaded.

**Describe the solution you'd like**
Add a `ENV_VAR` which can be set, which then asks blenderproc to check if the given file path, was used before if it was not used before load the file normally and create a `.blend` file, then the next time this blend file will be loaded instead of the original file.