CRM_Utils_File::findFiles should sort files alphabetically

There are certain situations where it would be nice if we could rely on CRM_Utils_File::findFiles to return the files it has found in alphabetical order.

For example if we knew the order that _hook_civix_civicrm_managed was going to return files matching *.mgd.php, it would provide a way around the limitation mentioned under limitations in https://civicrm.org/blog/totten/api-and-art-installation (when "you need to create a sequence of related entities").

managed-entities-1.mgd.php:

//create an entity

managed-entities-2.mgd.php:

// api getsingle the entity created in managed-entities-1.mgd.php
// create entity with details from created entity