I've been able to write a custom DataType implementation for Moment.js but am stuck in places where the equality of two instances of the DataType is evaluated.

Currently, there are a number of lines of code which specifically handle Dates differently because of their inability to be compared using ===. For instance, in a35_defaultPropertyInterceptor.js:

// exit if no change - extra cruft is because dateTimes don't compare cleanly.
if (newValue === oldValue || (dataType && dataType.isDate && newValue && oldValue && newValue.valueOf() === oldValue.valueOf())) {
return;
}

However, that means if I want a custom DataType, and need a custom equality operator, I have to edit this portion of the file. Instead, I propose using the `getComparableFn` method already available:

// exit if no change - extra cruft is because dateTimes don't compare cleanly.
var normalize = dataType && DataType.getComparableFn(dataType);
if (newValue === oldValue || (dataType && normalize && normalize(newValue) === normalize(oldValue)) {
return;
}

This would be similar to what you're doing in `getComparer` in `OrderByClause` in a45_entityQuery.js. One could use the same logic for the `coEquals` function in `EntityType` in a40_entityMetadata.js.

The other oddity I found while doing this was the custom code used for Dates in `fromJSON` in `DataProperty`. This function would seem better served by using the `parse` function of the dataType itself, or the static `DataType.parseRawValue`.

Finally, it would be nice to be able to attach a `getConcurrencyValue` function to `DataType` for use in `updateConcurrencyProperty` in `a50_entityManager.js`.