Mip-Mapping for zoom-out

Useful snippets:
```
auto glGenerateMipmap = (void(*)(GLenum))glfwGetProcAddress("glGenerateMipmap");
assert(glGenerateMipmap);
```
```
glBindTexture(GL_TEXTURE_2D, idTex);
    glTexImage2D(GL_TEXTURE_2D, ...)
    glGenerateMipMap(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, 0);
``` 