PHP scripting block in shorthand format

We use short tags a lot. While they might cause some errors with the initial setup, they shorten a decent part of our code... using <?= is a lot easier than <? echo.

You should be able to enable this in your PHP config: http://php.net/manual/en/ini.core.php#ini.short-open-tag

Hi - please see http://cern.ch/aelwell/scratch/concerto_short_tag_fixup.patch

This was generated in response when I couldn't use short tags.

(from [1b5b50c695dba19dce069733c1c662f29d88569a]) Cache the template preview, closes #58 PHP scripting block in shorthand format.

Wrapping the template preview code in a stale? block to only render and return the image if the etag doesn't match or there has been a modification.

Templates now can find the last_modified time of not just the template but also it's positions and background too in the event those update.
https://github.com/concerto/concerto/commit/1b5b50c695dba19dce06973...