Make oscillator scales scalable

Expand/contract the vertical scvale for osc windows, like we can for price scale on the main chart.

Reason: a period of high PA movemnet can cause wide values in an osc. After PA returns to normal volatility, the osc appears almost flat due to the auto scaling of the osc being set to accommodate the previous wide range. This remains in play until enough bars are drawn to push the past wide osc values off the left hand side of the chart.