TODO

- [0/3] bugs
  - [ ] last Pointer is NaN in search valid target
  - [ ] prevent infinite recursion
  - [ ] bootstrap example jumps up on drop
    - (only sometimes. preventDefault() does not work if called inside drop or on containing element. Look up where the on handler attaches itself)
    - only firefox, chrome works
- [0/6] consider
  - [ ] better name for searchValidTarget
  - [ ] shortcut on getNearest()
    - [ ] if items, break if distance is growing again
    - [ ] if containers, break if distance is 0
  - [ ] only calculate top/bottom if vertical and left/right if horizontal
  - [ ] support placeholder with height/width
  - [ ] calculate item/container dimensions relative to the container => Not all centers have to be recalculated
  - [ ] change subContainers handling, so that it becomes easier to remove them