Frontend changes

[jellewie]

• Take MaxGlassSize into account when requesting a drink. do not allow a request which has a higher fluid count than MaxGlassSize (The machine will give you an error back, and not make the drink). Frontend now has an "Please select a value that is no more than 1000" warning. Would be nice if this is dynamically. We could also show the '400' status message instead (This way the screen keeps being in front and you can adjust the drink to fix it for any error)