Fix bad interactions between retain points multiplier, as-needed dropping, and variable depth tile pyramids

2.60.0

• Fix bad interaction between --retain-points-multiplier and stopping early when the tile feature limit is reached
• Fix another bad interaction between --retain-points-multiplier, dropping-as-needed, and variable depth tile pyramids
• Add optional BUILD_INFO string to version
• Reorder overzoom logic to clip before dealing with multiplier and filters
• When --generate-variable-depth-tile-pyramid is in use, report the actual highest zoom generated as tileset maxzoom