====== behavior: progress ======
Progress indicator.   
===== Elements =====
that have this behavior applied by default (see [[master style sheet]]): 
  *  ''<progress />'' - inline element (from HTML5) 
  *  ''<input type="progress" />'' - inline 
  *  ''<widget type="progress"></widget>'' - block level element

===== Attributes =====
that this behavior knows about:
  *  ''value=float'' - initial value of the input element
  *  ''maxvalue=float'' - maximum value of the element.

===== Events =====
  N/A

===== Value =====
type json::value::V_FLOAT, read and write.


===== Special key combinations =====

  N/A (passive element)

===== Layout =====

Draws foreground image with respect of current value.
If value=100 and maxvalue=100 then foreground image covers background area in full.