Sketcher UX improvements

Multiple small improvements needed in sketcher 1) when adding constraints, if points / lines etc are selected when applying the constraint, use those rather than forcing the user to select the points or lines AFTER invoking the constraint. In fusion, you can select the things first, then apply the constraint, or invoke the constraint and then select the points. In solvecraft, you're forced to select the things to constrain after choosing the constraint. This same behavior actually applies to many operations, such as projecting external geometry to list another. Allow the external geometry to be selected first, then hit 'p' for project. In general, allow the operands to be selected BEFORE the operation and have it work. 2) when placing dimensions, have the dimension indicator pop up and follow the mouse until the user clicks to define where they want the dimension to be drawn, the same way it works in fusion. Having no feedback after clicking the thing to dimension is confusing, having to click a second time to actually get the dimension to appear. 3) It doesn't correctly add a coincidence constraint between two lines if I select them after hitting the coincidence constraint. It says "unknown sketch point 'l7' " or similar. It correctly creates the coincidence constraint if I drag one line on top of the other though. It seems coincidence you must select a point and a line, and it fails if you select 2 lines, which should also work. Just pick one of the points at the end of ...