ben blank <> in Gradle

Allow closures passed to LineFilter to remove lines by returning null. - LineFilter no longer implicitly tracks end of file via nullity of transformedLine, but explicitly tracks state (normal, line skip, eof). - Content of copyTestResources/src/two/two.b was unused, so now contains data for line removal integration tests. - Adding an entirely new test file would have affected tests which check which files were copied.