Fixes and rendering improvements!

[bryanedds]

Change list -

• Improved SSS significantly.
• Renamed ImNui to ImSim.
• Implemented Provide options to globally disable SSS. #1010.
• Nav file save error message fix.
• Making nav files writable when writing.
• Increased alpha of higher specular fragments for proper glass rendering.
• Made fineness much more authorable.
• Fixed inconsistent use of new form of scatter type iteration.
• Fixed Spot light SSVF artifacts at the end of light range. #1012.

Full Changelog: v18.13.0...v18.14.0

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This discussion was created from the release Fixes and rendering improvements!.