Investigate CQL expression evaluation optimizations

[rfecher]

For example, when a temporal predicate is provided profiling indicates that an overwhelming majority of time is spent in java.text.DateFormat.parse() for every call to CQLQueryFilter.accept(). It seems the call tree is using the geotools utility, DateConverter, to convert from String to Date, but it seems the result should be cached so that its not done repeatedly for every evaluation of the CQL expression (every simplefeature visited).