PLT-344 - Enhance TestHelper

Handle hidden serialization
Handle non-public enums
Add LocalDate factory for static import
PLT-344 - Data provider methods to be static
PLT-394 - Enhance Frequency

Add checks for week/month based
Make final (and Tenor)
PLT-372 - Make extensible enum implementations less fragile

Constants in interface is fragile
Adding a toString() to subclasses caused the system to break
PLT-372 - Rename day count constants

Follow existing OpenGamma usage
PLT-407 - Add date adjuster

Simplifies use of TemporalAdjuster
PLT-406 - Add roll conventions

Influenced by FpML
PLT-372 - Enhance business day calendar
PLT-407 - Add business day adjuster

Combines business day convention and calendar