Extend readouts

[Gerry1135]

Add readouts for min and max heap usage for last GC cycle. Immediately after a GC store the current usage in min and max, each increase store current in max, display both values in window.

Add readout for time between last two GCs. Each time GC count increases by one record the time since the previous GC and store current time. If GC count increases by more than one then set time to 0.

Change U and FU readouts to R and P (for rendered and physics).

[Gerry1135]

Done in 1.0.0.7