Auto range merge

This pull request has a bunch of changes, mostly around multiple y-axes.
I can split this up into multiple pull requests, let me know what works best.

I added a RightClickEventGenerator
tools now have an option for "showButton"
I also created an auto_range tool that watches the x-axis, and makes sure that the y-range can accomodate all points in the y_field.

Feedback welcome.