Performance improvement in Tag.php

The getTags() method in Tag.php uses recursion to build the tag hierarchy. The problem with this is that many unnecessary queries are generated on the civicrm_tag table as the function performs its recursion.

We have implemented a new version of Tag.php which makes a single query to grab the contents of the civicrm_tag table, and we build the tree after iterating over the results.

This cuts down on literally hundreds of queries per HTTP request for any tag-related operations.

I am attaching the new version of Tag.php to this ticket.

The full path to the file is custom/php/CRM/Core/BAO/Tag.php