update docs for new country grid location

Also updates some dependencies.

vagrant/install-on-centos-7.sh

@@ -151,6 +151,13 @@ else                               #DOCS:
     cd $USERHOME                   #DOCS:
 fi                                 #DOCS:
 
+# When installing the latest source from github, you also need to
+# download the country grid:
+
+if [ ! -f data/country_osm_grid.sql.gz ]; then       #DOCS:
+    wget -O data/country_osm_grid.sql.gz http://www.nominatim.org/data/country_grid.sql.gz
+fi                                 #DOCS:
+
 # The code must be built in a separate directory. Create this directory,
 # then configure and build Nominatim in there: