support for viewParams vendor parameter in GetFeature XML model

Support for vendor parameter: viewParams in WFS GetFeature requests to support GEOS-5160:  http://jira.codehaus.org/browse/GEOS-5160 

Changes:
* Set EMF runtime for WFS 2.0 to 2.6 to allow compilation against EMF version specified in pom.xml
* Add viewParams attribute to GetFeature model for WFS 1 & 2
* Created a wrapper around EList to handle parsing the string parsed from the attribute into the requried List<Map> datatype by string splitting