Make waterliles placable on the surface of standing water.

Lilies will be rotated randomly on place, in the same manner as they're
usually generated.

Hold 'sneak' (usually shift) while placing to force them to follow your
facedir instead.

Liles will replace buildable_to nodes when placed, including themselves.
This will cause a loss of lilies if you just keep placing them over and
over, but this is intentional.

node_ownership, glomie's protection mod, and zeg9's protection mod are
accounted for, as are infinite item stacks (e.g. plain creative mode).

Also, compact the waterlily register node calls into a loop.