RichardH : css tweaks to gui
RichardH : Refactoring of ModelElement
RichardH : removed unused css link
RichardH : removed unused code
RichardH : moved ModelElement to core folder
RichardH : refactored ModelElement removed updateCoordinates()
RichardH : removed unused code
RichardH : renaming validators to coordinators
RichardH : fixed line connector bug