Create an 'update.sh' script skeleton, and update usage messages.

create.sh

@@ -15,10 +15,10 @@
 # Sanity checks
 if [ $# -ne 2 ]
 then
-    echo "Wrong number of arguments. Expecting:"
-    echo "  ./install.sh <dest_dir> @P@ "
-    echo "    dest_dir        directory in which project subdir will be created"
-    echo "    @P@             package name)"
+    echo "Creates a new project using lw-build-system."
+    echo "Usage: $0 path/to/projects @P@"
+    echo "    path/to/projects        directory in which project subdir will be created"
+    echo "    @P@                     package name"
     exit 1
 fi