perpendicularity constraint

bug fix for tangent to ellipse and arcofellipse using a construction line
Bug fix: Show/hide internal geometry not working for external geometry
Visualization of Internal alignment constraints
Constraint visualization

Equality for ellipses and arc of ellipses
Merge pull request #6 from abdullahtahiriyo/sketcher_testing

Sketcher testing
Merge remote-tracking branch 'origin/sketcher_testing' into sketcher-solver-iterlog