Added ForestManager class.

src/ac/ed/lurg/ModelMain.java

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

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

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

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

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

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

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

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

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

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

src/ac/ed/lurg/output/LpjgOutputer.java

src/ac/ed/lurg/types/LandCoverType.java