[galaxy-commits] commit/galaxy-central: jgoecks: Implement a data manager for trackster. Convert DataCache into a DataManager and use jQuery Deferred objects to move data management from the tile level to the track level. Implications of these changes include (a) callbacks are no longer needed when drawing tiles; (a) data is fetched before a tile is drawn; and (c) tile drawing is completely tracked so that actions can be taken after a track has been drawn.