Merge pull request #34 from OpenGamma/topic/PLT-513

PLT-513 Add Frequency.exactDivide()
PLT-503 Rename getDayCountFraction to yearFraction

Avoid use of "get" for calculation methods
PLT-514 Additional schedule methods

Check if schedule is term schedule
Normalize term schedule on construction
Extract stubs and regular periods more easily
Merge a schedule to form larger periods
LengthInDays of period
SchedulePeriod to subSchedule
PLT-492 Indices for Fx

Add FxIndex and standard constants
Represents daily published FX rates