Add parameter to dateQueryBuilder fn to change date value to desired format

Currently in CRM_Contact_BAO_Query::dateQueryBuilder(), it builds where clause for date field whose value(s) are considered in mysql format (YmdHis). This put a restriction on date columns like civicrm_financial_trxn.trxn_date which stores and operates on ISO format date values.

It can be resolved by introducing $dateFormat parameter for dateQueryBuilder() to format the date to desired.