fixed null pointer error when dispose() causes adjustZoomBounds() to be
called

Change-Id: I79a434247aec6137eb574c0b2a02596d10f24898
using console.error() for errors instead of console.log()

Change-Id: I80a025d9ebb856c13300ad7807e4f47e15fbdaa5
added IColumnStatistics.getMedian() and getSortIndex()

Change-Id: Ia173cbddab2d43f4cbd9ea3e3fd431e67484f928