Ruler updates for v2.0.0 - leave the ruler on page

[adamwulf]

• remove the hand button
• ruler button becomes a toggle to hide/show the ruler on the page
• Ruler is now a physical object that is always visible on the page, similar to Notes
• Ruler shows three touch points
• user can move the ruler with 1 finger
• user can move/rotate the ruler with 2 fingers
• user can move/rotate/adjust the straight/circle with 3 fingers

to adjust the circle, hold 2 outermost touch points with two fingers, and pull the 3rd touch point with a 3rd finger. those three points determine the circle/oval to use, very similar as they do with the pinch right now. If the 3 points are >= 90 degrees, it draws the ruler as a circle arc. if they're < 90 degrees, it makes an oval arc.

If the circle is small enough, it makes the ruler circle back on itself to be an entirely circular ruler.

this makes drawing a circle on the page much more obvious than the current ruler system, and makes the entire process easier to understand.