typeAhead: second implementation of typeAhead - user can customize LDAP queries.

TypeAhead.php: Reformat of various constants. Hard coded LDAP query replaced by one submitted via SIP.
KeyValueStringParser.php: Implemented explodeWrapped() - behaves like 'explode()' but will respect strings wrapped in quotes as no explodeable.
Ldap.php: New class to manage LDAP access.
AbstractBuildForm.php: Add attributes DATA_TYPEAHEAD_LIMIT, DATA_TYPEAHEAD_MINLENGTH. Parsing of FormElement.parameter.typeahead* parameter.