Silentsiege cleanups

• Brushes and patches cleanups (around 20% less brushes in total)
• Removed some weird lights along the walls, as voted in poll 385: https://imgur.com/a/fWUZG0g
• Changed a few _lightmapscale values from 0.01 to 0.25.
• Fixed a visible caulk at the top of the MH room: https://imgur.com/a/4T4PjhX
• More consistency in clip usage (still not perfect though)
• Fixed a bunch of texture issues: https://imgur.com/a/4cdlEHJ + https://imgur.com/oVRHrmR
• Fixed some oozing light from a wall corner: https://imgur.com/a/xeVmWOS
• More caulk
• Added a small light texture above the MA, as there was no obvious light source and it looked weird.
• Fix #185 (closed) and #186 (closed)