Evtech

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* Documentation fixes
* Added access to camera elevation

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* Documentation build fixes

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* Added ability to get shapely geometry of image bounds on ground
* Included example application for measuring height from an image

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* Added triangulation function
* Updated usage docs
* Fixed bug in project from camera

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* Added height from two points to camera class
* Added ray interesection with elevation

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* Added ray class
* Added project from camera to camera class