Changes to set in GAMS intensities from previous run, as starting point.  Also changes for dry matter, and some tidy-up.

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.