[columns,rows] Remove superfluous widget types, leave containers as Layouts.

columns.lua

@@ -2,9 +2,6 @@ local BASE = (...):gsub('columns', '')
 
 local Layout = require(BASE..'layout')
 
-local Columns = setmetatable({}, Layout)
-Columns.__index = Columns
-
 
 -- Advance position to next column,
 -- given current position, widget dimensions and padding.
@@ -12,8 +9,8 @@ local function columnadvance(x,y, ww,wh, padding)
     return x + ww + padding, y
 end
 
-function Columns.new(args)
-    local self = setmetatable(Layout.new(args), Columns)
+function Columns(args)
+    local self = Layout.new(args)
 
     self.advance = columnadvance
     self.prev = 'left'