Updates to fix gcamdata issue with allocation of forest land

[kanishkan91]

This fixes an issue with breaking out regions as a result of allocation of managed forests. To use this feature, the user should follow the steps outlined below,

1. Before breaking out a region set the constant aglu.USE_BEFORE_ADJUST_FOREST_FILE to FALSE
2. Now run up to chunk - module_aglu_LB123.LC_R_MgdPastFor_Yh_GLU. This can be done using driver(stop_after = "module_aglu_LB123.LC_R_MgdPastFor_Yh_GLU")
3. This will generate the file- L123.LC_bm2_R_MgdFor_Yh_GLU_beforeadjust in the gcamdata/outputs/ folder
4. Copy the contents of this file (generated in step 3) to a file gcamdata/inst/extdata/aglu/LDS/L123.LC_bm2_R_MgdFor_Yh_GLU_beforeadjust . Just copy the contents and don't replace the whole file i.e. make sure the metadata does not change.
5. Set constant aglu.USE_BEFORE_ADJUST_FOREST_FILE to TRUE
6. After this , reload gcamdata- devtools::load_all(".")
7. Now run driver or driver_drake as ususal