Fix broken error page ignoring

We have to check for the data() class, or controller's class
Merge branch 'bug/fix-broken-error-page-ignoring' into ignore-userdefinedform

Conflicts:
	code/DynamicCacheControllerExtension.php
Fix class checking
Merge pull request #18 from Focus-Flow/bug/fix-broken-error-page-ignoring

Fix broken error page ignoring
Merge pull request #17 from Focus-Flow/ignore-userdefinedform

Ignore UserDefinedForms from cache
API Ability to configure uncacheable pages by type
Merge branch 'master' of https://github.com/tractorcow/silverstripe-dynamiccache