2013.08.22 13:00 UTC+4 - Bug fixes + Code refactoring

Done much refactoring in whiteMath/Functions.

Fixed the bug in AnalyticFunction/AnalyticFunction.cs & AnalyticFunction/AnalyticFunctionHelper.cs
with the cotangent function (ctg) - ctg got replaced with @ctg@ and then tg was replaced with @tan@ - which obviously led to errors since the string @ctg@ contains tg, too.