Speed Limits tool full rewrite/refactor; Render overlay refactor

[kvakvs]

New Speed Limits UI

NOTE: SVG source for two types of Road Signs are text (XML) files, taking a few thousands of lines, contributing to a huge added lines count. And deleted lines are rather moved, not actually deleted, contributing to both added and removed counts.

U User Interface

• U atlas loading reworked, now sprites to be loaded can have different paths and sizes, not just different names
• U now does not require explicit stacking call for new controls and it is a setting of autoresizer.
• Texture loading code for speed limit overlay now uses MIP maps (smoothing small icons to look good).

Speed Limits & UI Changes

• SpeedLimits legacy tool was deleted and the code moved to new SpeedLimits tool.
• Overlay rendering for SpeedLimits now has its own renderer class
• SpeedLimit rendering code now does not perform click handling, and the logic is called later from tool LeftClick handler.
• Overlay DrawTexture calls now moved from TrafficManagerTool to their own Highlight class.
• Get/SetSpeedLimit are not using float? anymore, and there are enumerated types explicitly saying if its not set, or set to unlimited.
• Road signs redone in vector (SVG via Inkscape) for German-style signs and blue road defaults.
  
• Default speed limits now have new blue icons.
  
• Overlay now shows override speed limits, but if you hold alt, also shows default speed limits as small icons.
• Overlay now shows default speed limits, but if you hold alt, also shows default override limits as small icons.
  
• Road signs for speed limits have opacity fading with distance.
  

Other TODO

• Holding CTRL in priority tool shows all info overlays. Expected: Only those required for the tool.
• Overlays for Parking / Vehicle Restrictions disappeared, fix me (Hint: Renders in different coords, can be seen if you rotate the camera)
• Edit default speeds mode
• Button texture update on Toggle Edit Segment/Lane
• Button texture update on Edit Defaults/Edit Overrides toggle
• Nice buttons for speed palette
• MPH toggle should refresh the palette
• Clicking a speed icon should have different effect based on whether overrides or defaults are edited now
• Consider kmph/mph alternative units text under the selected button like in the old UI?
• Refreshing the palette/tool window should save the window position.
• Showing full screen/segment operation with/without shift is displayed inverse but works OK.

Also

Fixes #988