Added carbon demand from external file.

src/ac/ed/lurg/ModelConfig.java

src/ac/ed/lurg/ModelMain.java

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

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

src/ac/ed/lurg/country/crafty/CraftyCountryAgent.java

src/ac/ed/lurg/country/crafty/CraftyProdManager.java

src/ac/ed/lurg/demand/AbstractDemandManager.java

src/ac/ed/lurg/demand/CarbonDemandManager.java