Potential fixes and little improvements

• Move calculations from RenderScene to PreRender hook. (Potential fix of flickering)
  
• Do not perform calculations while being in the TARDIS; otherwise, it will cause rendering glitches.
  
• Make debugging available only when `sv_cheats` is set to 1

Improvements

• Proper method for detecting RenderBounds change. Resolved compatiblity issue with prop resizer addons.
  
• Bump fov multiplier in calculations from 0.6 to 0.75

Ignore doors

Optimization

• Add and use lookup tables instead of using Entity.GetTable, as this reduces CPU time.

Optimization & AABB -> RenderBounds

• Change AABB to RenderBounds, which is more accurate (this should resolve visibility issue with striders, etc.)
  
• Reduce CPU time, optimize distance calculations

Improvements

• Reduce C calls
  
• Compatibility with RT cameras
  
• Ignore entities with "NoDraw" set to true on spawn.

Initial addon creation.