RFR: Refactoring changes for supporting typed points

I was working on creating a HistogramRollup and it appeared having two methods for Rollup like

a) computeFromRawSamples(Points<SimpleNumber>)
b) computeFromRollups<Points<Rollup>) made more sense.

Also, @fourk had a good comment in my previous PR that using Points\<Object\> to represent raw samples is bad. He wanted a strong typed Points<> class. So I am introducing a class SimpleNumber (I don't like the name but using Number causes collision with java.lang and I don't want to use fully qualified class names). Maybe NumericMetric is a better name for that class?

The upshot of using something like SimpleNumber is

java.lang.ClassCastException: com.rackspacecloud.blueflood.types.SimpleNumber cannot be cast to com.rackspacecloud.blueflood.types.BasicRollup
	at com.rackspacecloud.blueflood.types.BasicRollup.computeFromRollups(BasicRollup.java:118)
	at com.rackspacecloud.blueflood.types.AverageTest.testAddRollup(AverageTest.java:148)

However, due to the way generics are  implemented in java, type erasure happens and there is no run time validation of the type implicitly. Also, someone could just do Points points = Points\<SimpleNumber\> typedPoints. There is no way of getting around it. But there is definitely an advantage in using typed Points class.