filter: cleanup and add var {!=,<,<=,>,>=} var support
filter: cleanup and add var {!=,<,<=,>,>=} var support

Loop over str, int and dbl to generate code for matching.  Use thetajoin
and kdifference for implementing != and the rest.

zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb