add clang-tidy

This commit implements a clang-tidy file, and makes some changes to get
it to pass.  Most changes are naming or mechanical in nature.

Tested:
Clang-tidy now passes.

Signed-off-by: Ed Tanous <ed@tanous.net>
Change-Id: Ia441e4801b6c8725421d160c531c5df141f255d4
diff --git a/src/ExternalSensorMain.cpp b/src/ExternalSensorMain.cpp
index 9067d7e..19b8f60 100644
--- a/src/ExternalSensorMain.cpp
+++ b/src/ExternalSensorMain.cpp
@@ -43,7 +43,7 @@
 // there is no other way to tell, and it will be used for the object path
 // here: /xyz/openbmc_project/sensors/<Measure>/<Name>
 
-static constexpr bool DEBUG = false;
+static constexpr bool debug = false;
 
 static const char* sensorType =
     "xyz.openbmc_project.Configuration.ExternalSensor";