Fix null comparison in RelationalOperations
Change return type of RelationalOperations eq and neq to boolean

Not sure why the return type was Object, boolean can always be assigned to Object thanks to coercion?
Test for issue #75
Merge pull request #74 from supergillis/master

Fix null comparison in RelationalOperations
Fix for issue #75.
Merge pull request #81 from lyncodev/issue75

"is" operator to support selection expressions