Change annotation line widths from "pixel thickness" to "percentage of...

Change annotation line widths from "pixel thickness" to "percentage of viewport height thickness".  That is, the thickness of a line is a function of the height specified by the user and the height of the viewport in which the line is drawn.  However, the minimum and maximum thickness is dependent upon the implementation of OpenGL.  On Mac, the maximum thickness is 10 pixels so lines will stop growing in thickness fairly quickly.