various: encapsulate all code in the olive namespace to avoid name collisions

Large-scale code cleanup. Also adds a license to the top of all files that were
missing it.

app/common/timecodefunctions.h

@@ -25,6 +25,8 @@
 
 #include "common/rational.h"
 
+OLIVE_NAMESPACE_ENTER
+
 /**
  * @brief Functions for converting times/timecodes/timestamps
  *
@@ -68,4 +70,6 @@ public:
 
 };
 
+OLIVE_NAMESPACE_EXIT
+
 #endif // TIMECODEFUNCTIONS_H