Implied Vol

Function Implied Vol within Tradable returns the implied volatility of the given tradable and its corresponding price.
This is the volatility that results to a price that matches the provided target price.
For now, the valuation algorithm cannot be specified by the user.
It is hard-coded to be the analytic Black Scholes Merton for europeans and the Finite Differences Crank Nicolson for bermudans and americans.