Fix for gxp #189 - allow matchCase in WFS Filter

See description in issue #189. With this fix the QueryPanel gets an extra config param 'caseInsensitiveMatch' (default false) to allow case-insensitive string matching for attribute conditions in OL ComparisonFilter's. This setting propagates to an OpenLayers WFS Filter attribute 'matchCase'.

See a working example here:
http://lib.heron-mc.org/heron/latest/examples/querybuilder
- select USA States layer
- add STATE_NAME = condition
- fill in e.g. ohio or alabama
- see one result