split parameters for logging and tuning

add a flag to enable/disable tuning: default off
add an option for specifying a folder for outputting logs.

Closes: #10
Signed-off-by: Patrick Venture <venture@google.com>
Change-Id: I43864768f1dee8672f13288d3cf5a0c87c373aed
diff --git a/pid/tuning.hpp b/pid/tuning.hpp
index 511c797..ba4ec32 100644
--- a/pid/tuning.hpp
+++ b/pid/tuning.hpp
@@ -2,8 +2,12 @@
 
 #include <string>
 
-/** Boolean variable controlling whether tuning logging output is enabled
+/** Boolean variable controlling whether tuning is enabled
  * during this run.
  */
-extern bool tuningLoggingEnabled;
-extern std::string tuningLoggingPath;
+extern bool tuningEnabled;
+/** String variable with the folder for writing logs if logging is enabled.
+ */
+extern std::string loggingPath;
+/** Boolean variable whether loggingPath is non-empty. */
+extern bool loggingEnabled;