moved Length functions from java to js
added conversion table to Length.js
added Area and Volume js classes
renamed files and added test page
fixed multiply functions on Length and Area; added new square and cube functions on Length
moved Circle functions from java to js; fixed script tags on test page
converted Cylinder.java to Cylinder.js
converted Polygon.java to Polygon.js
converted Quadrilateral.java to Quadrilateral.js
converted Parallelogram.java to Parallelogram.js
converted Rectangle.java to Rectangle.js
converted Rhombus.java to Rhombus.js
converted Square.java to Square.js
added '@extends' in comments
converted RectPrism.java to RectPrism.js