Incorporate DATE type into Filter Builder

[GoogleCodeExporter]

How OpenLayers reads/writes date functions is a bit more complicated than 
originally thought. However, it should be possible to:

* get the OpenLayers parser working nicely with the GeoServer "dateParse" 
function so that filters can be generated correctly
* get the filter parsing code to "read back in" the "dateParse" filters and set 
values accordingly
* create a "date-picker" from the Ext code to allow the user to pick the start 
and end dates

This would enable MassGIS to not have to convert DATE types to numeric to do 
date comparisons.  It would same some data massaging time. 

Original issue reported on code.google.com by Aleda.Fr...@state.ma.us on 22 Jun 2012 at 1:22

[MassGIS]

Aleda 11/12/2015 - would need a sample datalayer to test on that has real dates.
On 6/21/2012 Charlton commented in email: "Applying that is the kiss of death for our OpenLayers FILTER approach. It doesn’t have the concept of an ogc:Function.

So not only would we need to stick that in the FILTER manually, we’d have to add a dateField type to the filter builder for it to distinguish a number from a date and know when to apply this extra tag."

Sounds like this is quite difficult and not in demand right now so setting priority down to low.