Added land cover conversion cost.

GAMS/IntExtOpt.gms

debug_config.properties

src/ac/ed/lurg/ModelConfig.java

src/ac/ed/lurg/country/CountryAgent.java

src/ac/ed/lurg/country/gams/GamsLocationOptimiser.java

src/ac/ed/lurg/country/gams/GamsRasterInput.java

src/ac/ed/lurg/country/gams/GamsRasterOptimiser.java

src/ac/ed/lurg/landuse/ConversionCostReader.java

src/ac/ed/lurg/landuse/WoodYieldReader.java