Add property for wrapperTpl

Added functionality for a wrapper template chunk. This makes it easier to use getImageList in this situation:

[[
  [[*showList:is=`1`:then=`
    getImageList?
      &tpl=`teaser_kacheln_migx_tpl`
      &tvname=`teaser_kacheln`
  `:else=`-`]]
]]

...with a wrapperTpl you can now add container markup etc easily.