title: How to wrap and stack items in QML, into rows and columns
body: <p>I have a series of buttons that I want to appear in columns at the bottom of my QML page.  The number of columns across should depend on the width of the window, as the window width increases I want more columns to be added.  (And fewer rows as a result as components are pulled up to the previous line)</p>
  <p>This is sort of like a Flow component, but I want the items to appear in columns, evenly spaced across the page, in rows and columns (columns centered vertically, at the bottom of the page).  Sort of like GridLayout.</p>
  <p>I can't figure out what QML component(s) to use to achieve this.</p>