added warning for unsaved layers, added linear structures dialog, toolbar buttons for add and edit linstructs, made more UI options persistent
added warning for unsaved layers, added linear structures dialog, toolbar buttons for add and edit linstructs, made more UI options persistent

nakijun/vtp,nakijun/vtp,seanisom/vtp,markraz/vtp,nakijun/vtp,markraz/vtp,seanisom/vtp,markraz/vtp,seanisom/vtp,markraz/vtp,seanisom/vtp,nakijun/vtp,seanisom/vtp,markraz/vtp,nakijun/vtp