fix(lua) - Store and update the 'zone' rectangle for Lua widgets.

[philmoz]

Fixes #2598

Summary of changes:

Implements solution from @jfrickmann in issue 2598:

• Store the widget zone rectangle data in the Lua registry.
• Updates the zone data when the layout changes.

Also calls the widget 'update' function if the zone has been altered.

[pfeerick]

This is working beautifully with the sample widget code which was provided in #2598 ... i.e. w and h update automatically as changes are made that affect them.

local defaultOptions = {}

local function create(zone, options)
  return {zone=zone, options=options}
end

local function update(wgt, newOptions)
end

local function background(wgt)
end

local function refresh(wgt, event, touchstate)

  local st = string.format ("w=%s, h=%s, event=%s", wgt.zone.w, wgt.zone.h, event)
  lcd.drawText (wgt.zone.x, wgt.zone.y, st, SMLSIZE)
  lcd.drawRectangle (wgt.zone.x, wgt.zone.y, wgt.zone.w, wgt.zone.h)
end

return { name="paneinfo", options=defaultOptions, create=create, update=update, refresh=refresh, background=background }