Improvments to CQL/ECQL parsing with regard to date/dateime parsing. #147

- modified grammer adding TEQUALS operator
- modified grammer to allow for date literals in regular binary comparison (ECQL)
- fixed some issues with regard to timezone offset handling
- made date/time/timezone extraction more robust with regular expressions
GEOT-4411 - added some examples to user guide for cql TEQUALs and ecql datetime literals