Contants.cs : Classes changed for Enumeration form stronger typed procedure calls
ForecastIORequest.cs : Modified to suite Enumeration
RequestHelpers.cs : Idem + simplification of procedure FormatExcludeString
Merge pull request #3 from VibertJ/2d3e0b8ef93f927dcc75fce133bbdfe43175b671

Constants updated to use strongly typed classes.