deleted KCollectionFragment since its constructor is never called anyway
included pcollections jar

Conflicts:

	src/javasources/KTool/.classpath
	src/javasources/KTool/buildjava.xml
refactored to use cons-list as the internal data structure for KSequence; simplified CopyOnWriteTransformer#transform(KSequence)
removed unnecessary defensive copying before calling the constructor of KList
forgot to remove code that are commented out
applied serialization proxy pattern to KSequence
merged with unified-builtins2 branch
Merge pull request #551 from yilongli/use-cons-list-in-ksequence

Use cons list in ksequence