various edit tool fixes

* **change selection and highlights to use axis aligned bounding box** - the tool was showing the rotated bounding box, but that was confusing since the grab handles were on the axis aligned box... this PR reconciles that difference
* **don't click through grab handles** - we were accidentally allowing the grab handles of a selected object to be "clicked through" to select an object behind the current selection. that was not desired.
* **don't allow stretching below a minimum dimension** - if you try to stretch below a minimum dimension it will clamp to that minimum
* **handle unselect** - by clicking in space correctly unselect
* **don't show hover highlight when in a tool** - we were showing the hover highlight while using tools like rotate and stretch - that was not desired
* **fix shifting tickmarks** - the tick marks were moving if you used start/end points