Get informations about in which slot a block is listed form properties.
Implment storing the slot per block. Move slot related code into the slot.py.
Connect simplelayout slots (jquery ui sortable).
Reload masonry on all simplelayout slots. The block may have changed the slot.
Adjust sortable for a better d'n'd experience.
Fix adding blocks if there is more than one slot.
BugFix: No longer disable img resizable while resize the block.
Merge pull request #16 from 4teamwork/mle-slots

Implement dragging between multiple slots.