Set things up to implement HTTP query for preaggregates

* expose a method in `NumericSerializer`
* fix `hasData()` bugs in (see https://github.com/rackerlabs/blueflood/issues/229)
* `NUMERIC` marker data type to indicate non-string + non-boolean.
* expose type of contents in `Points`.
* treat empty the same as null in `RollupType.fromString()`
log errors in `HttpRollupsQueryHandler`
reader reads from proper CF during rollup by ascertaining rollup type.
Handle the new rollup types properly on query

PlotRequestParser - Have a set of defaults for each rollup type, and a special marker set that indicates the default set should be used.
RollupHandler - Use generic `Points` instances and a utility method to compute `Points`->`Rollup`.
BasicRollupsOutputSerializer - add stats for various other fields, extract by rollup type (some extractions are invalid).
JSONBasicRollupsOutputSerializer - convert general default filter to type-specific default filter. add `toJSON()` conversion cases for the new types. make `getFilteredStatesForRollup` a moar generic.
Merge branch 'master' into aggregate_query
flatten the percentiles dictionary for timers.
count needs to be set when there is a latest value.
tests for JSON serialization of new rollup types.
Merge branch 'master' into aggregate_query
Add the test for RollupTool
Fix some nits
Making the integration test pass
Change the IntegrationTest name to actually mean it
get rid of DataType.NUMERIC.
Fix some nits and change test to assert
Merge pull request #221 from chinmay-gupte/chinmay/testRollupTool

Test for Rollup Tool
Add s RollupEventSerializer to core, Use that in Kafka serializer wrapper
Start sending timestamp of rollup along with RollupEvent
Merge pull request #185 from chinmay-gupte/make_serializer_generic

RFR : Add support for Rollup types like Histogram/Timer/Counter to the Kafka Serializer
change back to where `hasData()` uses `sampleCount`.