Add local variables centerTop, centerLeft in drawShape()
Return an empty array for a total of zero tiles
Add utility method warn() for warnings

The method prints messages to the console using console.warn()
when available, and does nothing otherwise.
Add warnings for unsupported values found in layouts

I tracked a nasty bug which was caused by the use of the
value 'top' for the property 'align', where it has no meaning:
'top' is only supported for the property 'valign'.

The warnings will help to detect and avoid this kind of issue
in the future.
Fix alignment of WG2+3 in Working Group in Assessment Reports Category

This misconfiguration prevented the WG2+3 from being displayed
in this configuration.
Merge branch 'master' into gh-pages