sensors: split building from manager object

To increase testability, split out the building of sensors
from the sensor manager.  And this further splits out building
from a configuration file.

Tested: Verified code continued to build and link.
Tested: Ran on quanta-q71l board and it behaved as expected.

Change-Id: Ib63a11e1107b1864c3c370bba2bd9ef2effa42f3
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/sensors/builder.hpp b/sensors/builder.hpp
new file mode 100644
index 0000000..2849c71
--- /dev/null
+++ b/sensors/builder.hpp
@@ -0,0 +1,15 @@
+#pragma once
+
+#include <map>
+#include <memory>
+#include <string>
+
+#include "sensors/manager.hpp"
+#include "sensors/sensor.hpp"
+
+/**
+ * Build the sensors and associate them with a SensorManager.
+ */
+std::shared_ptr<SensorManager> BuildSensors(
+    const std::map<std::string, struct sensor>& config);
+