Sand hourglass works. Broke API for previous projects, particularly re forces and triangle lattice (removed sled force entirely). +Force base class.
Changed bounds to allow min/max for each dim and used in hourglass. +Hourglass wall force accounting (alpha in plot and dump to CSV).
Fixed anchors interacting (they shouldn't; np arrays sometimes make copies when you don't expect it).
+Flux-type measurement in stats and CSV. Fixed container bounds and other proportions (figsize, etc).
+Properties for container bounds. +Helpers for making dirs and finding distances.
Changed directory of animation files and default colors. Fixed error saving anim due to non-integer figsize.