Trade barriers dummy file.

Change trade barriers to affect imports rather than exports.
Created 'TradeManager' to allow for switching on and off of barriers from file.

incorporating trade barriers. trade barriers only affect exports. rather than calculate global export calculate country export (global export * scaler for country). Parameter in GAMS still called worldExportPrice. Perhaps needs to be changed to country.

protected area (Mha) setters and getters and alteration to getSuitable to ensure protected land is not passed to GAMS

overload divideBy method to divide by an int, used for getting mean trade barrier value for composite countries