added feature to snap at midpoint while using path tool#3766

krVatsal wants to merge 3 commits intoGraphiteEditor:masterGraphiteEditor/Graphite:masterfrom

krVatsal:shift-key-snaps-lines-from-middle-for-shpeskrVatsal/Graphite:shift-key-snaps-lines-from-middle-for-shpesCopy head branch name to clipboard