[PLAT-6820] Generic Implied Volatilty Solver
[PLAT-6821] Bjerksund Stensland model fails for zero volatility

Have also remove BjerksundStenslandModelDeprecated and related tests.
[PLAT-6821]  Bjerksund-Stensland model fails for zero volatility. Remove final a restore jacadocs formatting.
[PLAT-6821] fix build error
[PLAT-6820] Remove commented out code
[PLAT-6821] Removed BjerksundStenslandModelFunction
[PLAT-6821] Added zero vol coverage
Merge pull request #242 from OpenGamma/topic/PLAT-6820

Topic/plat 6820