Adds an easy way to install the map merge driver

Fix the mapmerger bat paths

tools/mapmerge/clean_map.bat

@@ -1,5 +1,5 @@
-set MAPFILE=tgstation.2.1.3.dmm
+set MAPFILE=TgStation/tgstation.2.1.3.dmm
 
 java -jar MapPatcher.jar -clean ../../_maps/map_files/%MAPFILE%.backup ../../_maps/map_files/%MAPFILE% ../../_maps/map_files/%MAPFILE%
 
-pause
+pause

tools/mapmerge/install.txt

@@ -8,7 +8,9 @@ Committing
 This will make sure in the new version of your map, no paths are needlessly changed, thus instead of 8000 lines changed you'll get 50 lines changed. This not only reduces size of your commit, it also makes it possible to get an overview of your map changes on the "files changed" page in your pull request.
 
 Merging
-The easiest way to do merging is to install the merge driver. For this, open -tg-station/.git/config in a text editor, and paste the following lines to the end of it:
+The easiest way to do merging is to install the merge driver. For this, you can just double-click "install_driver.bat" in the tools/mapmerge/ directory.
+
+Alternatively, open -tg-station/.git/config in a text editor, and paste the following lines to the end of it:
 
 [merge "merge-dmm"]
 	name = mapmerge driver

tools/mapmerge/install_driver.bat

@@ -0,0 +1,7 @@
+@echo off
+echo. >> ../../.git/config
+echo [merge "merge-dmm"] >> ../../.git/config
+echo	name = mapmerge driver >> ../../.git/config
+echo	driver = ./tools/mapmerge/mapmerge.sh %O %A %B >> ../../.git/config
+echo. >> ../../.git/config
+

tools/mapmerge/prepare_map.bat

@@ -1,4 +1,4 @@
-set MAPFILE=tgstation.2.1.3.dmm
+set MAPFILE=TgStation/tgstation.2.1.3.dmm
 
 cd ../../_maps/map_files
 copy %MAPFILE% %MAPFILE%.backup