Add plot type "power" and Watt format.

Note that this technically breaks backwards compatibility of trace files
for 0.9.2 builds. But, whatever, as it's not yet released.

public/tracy/TracyC.h

@@ -16,6 +16,7 @@ enum TracyPlotFormatEnum
     TracyPlotFormatNumber,
     TracyPlotFormatMemory,
     TracyPlotFormatPercentage,
+    TracyPlotFormatWatt
 };
 
 TRACY_API void ___tracy_set_thread_name( const char* name );