This PR does two things:

1. I moved `package.json` into the root directory. Why? We are using `npx` from the `Makefile` which is executing usually under the root directory. If we install `node_modules` in `src/js` then these invocations don't see `node_modules` and install an extra copy of the packages. So we want `node_modules` in the root directory. node wants to put `node_modules` in the same directory as `package.json` hence I moved `package.json`. I also updated the build rules so that any recipe that uses `npx` has a dependency on `node_modules/.installed`.
2. We invoke `file_packager.py` from both the Makefile (in two places) and from `build_pkg`. There has been some drift in which options are applied in the two places. I extracted the common options and the task of locating the `file_packager.py` script into `tools/file_packager.sh`. I also shortened the make rules for `distutils.data` and `test.data` and made some minor updates to the dev docs about `file_packager.py`.
MAINT Improvements to node and file_packager invocations. This PR does two things:

1. I moved `package.json` into the root directory. Why? We are using `npx` from the `Makefile` which is executing usually under the root directory. If we install `node_modules` in `src/js` then these invocations don't see `node_modules` and install an extra copy of the packages. So we want `node_modules` in the root directory. node wants to put `node_modules` in the same directory as `package.json` hence I moved `package.json`. I also updated the build rules so that any recipe that uses `npx` has a dependency on `node_modules/.installed`.
2. We invoke `file_packager.py` from both the Makefile (in two places) and from `build_pkg`. There has been some drift in which options are applied in the two places. I extracted the common options and the task of locating the `file_packager.py` script into `tools/file_packager.sh`. I also shortened the make rules for `distutils.data` and `test.data` and made some minor updates to the dev docs about `file_packager.py`.
The original source files are missing some imports. gcc assumes implicit
function declaration, so the code compiles fine, but emscripten sets
 -Werror=implicit-function-declaration so it is a hard error.

--- a/BLAS/SRC/xerbla.c
+++ b/BLAS/SRC/xerbla.c
@@ -10,6 +10,8 @@
 		http://www.netlib.org/f2c/libf2c.zip
 */
 
+#include <stdio.h>
+
 #include "f2c.h"
 #include "blaswrap.h"

--- a/INSTALL/tstiee.c
+++ b/INSTALL/tstiee.c
@@ -10,6 +10,8 @@
 		http://www.netlib.org/f2c/libf2c.zip
 */
 
+#include <string.h>
+
 #include "f2c.h"
 #include "blaswrap.h"


The original source files are missing some imports. gcc assumes implicit
function declaration, so the code compiles fine, but emscripten sets
 -Werror=implicit-function-declaration so it is a hard error.

--- a/BLAS/SRC/xerbla.c
+++ b/BLAS/SRC/xerbla.c
@@ -10,6 +10,8 @@
 		http://www.netlib.org/f2c/libf2c.zip
 */
 
+#include <stdio.h>
+
 #include "f2c.h"
 #include "blaswrap.h"

--- a/INSTALL/tstiee.c
+++ b/INSTALL/tstiee.c
@@ -10,6 +10,8 @@
 		http://www.netlib.org/f2c/libf2c.zip
 */
 
+#include <string.h>
+
 #include "f2c.h"
 #include "blaswrap.h"

