[PLAT-6777] Fixed coupon stub in annuity builders

Also includes [REQS-648] Added tests for stub handling

Conflicts:
	projects/OG-Analytics/src/main/java/com/opengamma/analytics/financial/instrument/annuity/AbstractAnnuityDefinitionBuilder.java
	projects/OG-Analytics/src/main/java/com/opengamma/analytics/financial/instrument/annuity/FloatingAnnuityDefinitionBuilder.java
	projects/OG-Analytics/src/test/java/com/opengamma/analytics/financial/instrument/annuity/FixedAnnuityDefinitionBuilderTest.java
	projects/OG-Analytics/src/test/java/com/opengamma/analytics/financial/instrument/annuity/FloatingAnnuityDefinitionBuilderTest.java