dfrec: Initial implementation

This module implements support for the DFRobot EC (Electrical
Conductivity) meter.  It relies on the use of the DS18B20 UPM C module
for temperature gathering.

It has a pretty complicated calibration procedure which is somewhat
documented on the DFRobot wiki.  Functions have been added to support
changing the various coefficients as desired.

Signed-off-by: Jon Trulson <jtrulson@ics.com>

src/dfrec/jsupm_dfrec.i

@@ -0,0 +1,13 @@
+%module jsupm_dfrec
+%include "../upm.i"
+%include "std_string.i"
+%include "cpointer.i"
+
+/* Send "int *" and "float *" to JavaScript as intp and floatp */
+%pointer_functions(int, intp);
+%pointer_functions(float, floatp);
+
+%include "dfrec.hpp"
+%{
+    #include "dfrec.hpp"
+%}