MODE-2250 Fixed the handling of negative (-1) depths for the REST service when retrieving items.

Conflicts:
	web/modeshape-web-jcr-rest-war/src/test/java/org/modeshape/web/jcr/rest/ModeShapeRestServiceTest.java
Merge pull request #1171 from hchiorean/MODE-2250

MODE-2250 Fixed the handling of negative (-1) depths for the REST service when retrieving items.