NCX: change all @id attributes to correct data type "ID"
tests for NCX ID's and issue #313
Merge pull request #318 from IDPF/issue/313

Changes to ncx.rng schema and tests
stylesheet links in XHTML should be checked case-insensitive
Merge pull request #318 from IDPF/issue/313
ignore node.js files/folders also on master branch

useful when switching between contrib/nook and master
test file for issue #316 in wrong directory

references rev 50c49ff
Merge remote-tracking branch 'origin/master' into contrib/nook

Conflicts:
	src/main/java/com/adobe/epubcheck/ops/OPSHandler.java
	src/main/resources/com/adobe/epubcheck/schema/20/rng/ncx.rng
	src/test/java/com/adobe/epubcheck/api/Epub20CheckTest.java