CiviEngage installation fixes

Not sure what component to tag for CiviEngage stuff.

Step 4 of http://wiki.civicrm.org/confluence/display/CRMDOC32/CiviEngage+Installation led to bugs discussed http://forum.civicrm.org/index.php/topic,14937.0.html

I manually editted the CustomGroupData.xml.new file attached to remove the entries like CustomField <name> entries that would not port reliably to other installations when id numbers changed.

In a corresponding change, I modified the bin/migrate/import.php file to do lookups as appropriate when names, etc weren't provided in an xml file to import and other unique fields like labels or title were used.

Note that there is a separate but related patch to add a unique index to civicrm_uf_group at http://issues.civicrm.org/jira/browse/CRM-6590.

It seems the svn location of civicrm_engage has gone wandering... it was at http://svn.civicrm.org/tools/trunk/drupal/modules/civicrm_engage but I can't find it there now. That's why the new xml file is included rather than a patch.