Tidied up FiltersForm so it would resize nicely.
Fixed some rounding issues with image centering. The form now correctly mirrors by subtracting one from the image width. It also draws the marker in a way such that the pixel can actually be seen.

A RoundingPolicy has been added to SpriteImage to control how the center pixel is determined for images with even width or height. In this case the center straddles two pixels. Separate policies apply for X and Y directions, this allows the left and right images to have a policy that mirrors the X coordinate (Floor and Ceiling) but keep the Y coordinate in sync (with the default rounding mode of ToEven).
Removed follow cool-down and added a new behavior attribute for follow offset type. This type can specify that the offset be mirrored to match the target's facing. This has been applied to the conga interaction so that the ponies actually line up properly, rather than relying on nasty timing hacks.
Tweak mouse handling to properly account for dragging and cursor awareness settings in any combination of states. If dragging begins then any interaction running will be forcibly canceled among all target ponies and they will resume with a random behavior. If this happens a maximum 30 second delay is used rather than a full blown cool-down since the interaction didn't get to run its full duration.