Moonsighting Committee Worldwide Calculation Method

I contacted Khalid Shaukat from http://moonsighting.com/ and he provided me with the calculation method he uses. This calculation method is officially endorsed method by the masajid and scholars of London in creating the Unified London Time Table and by the Fiqh Council of North America. The full content of his email explaining the method can be found here https://gist.github.com/ameiralzoubi/638c76b69582d4f3bf89

As ITL can now calculate times using the Moonsighting Committee Worldwide method, I have changed back North America to 15/15, as the 17.5/15 value was an approximation of the MWC method. Users should use the new method to receive those times, and those still wishing to use the legacy value of 15/15 can still do so.

In addition to the above, a value was added to conf, extremeLat, to know at what latitude Fajr and Isha should always use the extreme method. Prior to this, the code was using nearestLat to determine this which was incorrect.