Position the control panel and units panel relative to the screen. Change the measuring tape initial position.
Added a play-pause button and relatively positioned the fluid density control slider.
Fixed the layout of the barometers container
Configure the sim renderer to be SVG.  Minor code refactor to the ruler node.
Fix the name of the 'x' icon
Use linkAttribute where possible
Use property.valueEquals where possible
Added some documentation to the ruler
Factored model specific stuff out of Units. Units is now "property free
" and can be used statically.