It should be possible to access basic properties:
* create new layers.
* delete layers
* name layers
* change layer state
** visibility
** alpha inheritance
** lock
** onionskinning
** layerstyles????
** alpha lock
** passthrough(for groups)
** layer blending mode
** opacity
* create clone layers of node.
* create masks
** filter?
** transparency? Via split alpha?
** transform masks?
For that matter, animation api?
Filtering:
* Filter by name
* filter by color label
* filter by type
* filter by layer state?