Added left and right min and max for y-axis

This adds the ability to set manual min and max values for each Y axis. A natural progression of this would be to split the axis edit panel, and only show the controls for the right Y axis when you're actually using it. Another nice improvement that could be made is having the datatype dropdown apply to the min and max values as well. Right now, if you want the max value to be 150MB, you have to enter "157286400" in the max value field.