dfrorp: Initial implementation

This module implements support for the DFRobot Analog ORP
(Oxidation/Reduction Potential) Meter.

It requires 5.0 volts, but the more accurate the voltage specified (to
the constructor), the more accurate the meter (paraphrased from the
wiki).

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

src/dfrorp/CMakeLists.txt

@@ -0,0 +1,9 @@
+upm_mixed_module_init (NAME dfrorp
+    DESCRIPTION "upm dfrobot analog ORP sensor"
+    C_HDR dfrorp.h
+    C_SRC dfrorp.c
+    CPP_HDR dfrorp.hpp
+    CPP_SRC dfrorp.cxx
+    FTI_SRC dfrorp_fti.c
+    CPP_WRAPS_C
+    REQUIRES upmc-utilities mraa)