Read MaxValue and MinValue from configuration

Read MaxValue and MinValue from enviroment variables file.
With this change MAXVALUE_temp1 and MINVALUE_temp1 for example
can be read from the configuration and added to dbus.

Change-Id: Ic7c2ba57ae65415bb154c617b13866d661969e5a
Signed-off-by: James Feist <james.feist@linux.intel.com>
diff --git a/mainloop.cpp b/mainloop.cpp
index 419bfc7..1cd5db6 100644
--- a/mainloop.cpp
+++ b/mainloop.cpp
@@ -237,6 +237,17 @@
         iface->scale(getScale(attrs));
     }
 
+    auto maxValue = getEnv("MAXVALUE", sensor);
+    if(!maxValue.empty())
+    {
+        iface->maxValue(std::stoll(maxValue));
+    }
+    auto minValue = getEnv("MINVALUE", sensor);
+    if(!minValue.empty())
+    {
+        iface->minValue(std::stoll(minValue));
+    }
+
     obj[InterfaceType::VALUE] = iface;
     return iface;
 }