[REQS-490] First draft of the inflation demo/tests.
[PLAT-490] Added US CPI data.
[REQS-490] Calibrated inflation curve and present value.
[REQS-490] Change hierarchy of PriceIndexCurve to introduce an interface.
[REQS-490] Added inflation curves with seasonality and known starting values.
[REQS-490] Added unit tests and argument checkers.
Merge branch 'develop' into topic/REQS-490

Conflicts:
	projects/OG-Analytics/src/test/java/com/opengamma/analytics/financial/provider/curve/CurveCalibrationConventionDataSets.java
	projects/OG-Analytics/src/test/java/com/opengamma/analytics/financial/provider/curve/CurveCalibrationTestsUtils.java
[REQS-490] Added argument checkers and corrected some doc.
Merge pull request #243 from OpenGamma/topic/REQS-490

Topic/reqs 490