Draft Line

This tool asks the user for 2 points and draws a line betwen them. The newly created line will have the current color and width. The points can be picked with the mouse in the 3d view or by entering corrdinates with the keyboard.

Usage
Following functionality is availible:
 * Picking a point on an empty area of the 3d view will return a point situated at your mouse location on the current workplane.
 * Picking a point on an object will return a point situated on the object, at your mouse location. An open "o" symbol appears to notify you.
 * Pressing CTRL will snap your point to availible snap locations. A filled "o" or square symbol appears.
 * Pressing SHIFT will constrain your new point in relation to the last one, horizontally or vertically, depending on the location of your mouse at the moment you press SHIFT. To change between horizontal and vertical, simply release SHIFT and press it again with your mouse in another location.
 * Enter numbers to insert manually a coordinate.
 * Pressing ENTER will switch you from X to Y, from Y to Z and pressing ENTER while you are editing Z will create a new point.
 * Pressing SPACE will switch between relative and absolute coordinates. In relative coordinates, the location you enter is relative to the last point.
 * Pressing CTRL+Z or pressing the "Undo" button will undo the last point.
 * Pressing ESCAPE will cancel the operation.