DDF-894 Added propertyIsNull support to the SolrFilterDelegate

-kind of odd to get this to work.  First you come in without a field type so we have to do so using the getAnonymousField() method.  Than we have to use the negative queries to actually get the results we need. (*:* -fieldName:[* TO *]) is the magic sauce to get this to work.  For details on how this works, visit the url below.
-http://stackoverflow.com/questions/17044661/how-to-filter-search-by-values-that-are-not-available/17045097#17045097
The above works fine on its own.  However, when you pair it with other expressions it doesn't return the correct results.

try this in the solr query console:

1.) -possibleField:[* TO *]   -- This should work fine. returns where possibleField IS NULL

2.) possibleField:someValue  -- This should work fine. returns where possibleField = someValue 

3.) -possibleField:[* TO *] OR possibleField:someValue  -- returns empty set.