Make ItemFactoryTest.java platform agnostic. Fixes BUKKIT-4695

Maven paths that include spaces (and possible other characters) get
improperly translated when using a file handle from a URL. This changes
the unit test to open a stream directly from the URL, providing proper
file resolution on multiple platforms.
Merge remote-tracking branch 'upstream/master' into sakura162

Conflicts:
	src/test/java/org/bukkit/craftbukkit/inventory/ItemFactoryTest.java