Plot: Show pointer coordinates and pass axis range to label functions

[s-nie]

I'd like to see the following changes in plots:

• An option to display the pointer coordinates in one of the plot corners, preferably also with a custom formatting function.
• Pass the corresponding axis range to the axis label functions. This is required to decide on the format and precision when formatting the axis values as timestamps.
• Rename the custom_label_func to label_formatter to be in line with the other methods x_axis_formatter, y_axis_formatter and coordinates_formatter (new)