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/widget/timeruler/timeruler.h

@@ -27,6 +27,8 @@
 #include "common/timerange.h"
 #include "seekablewidget.h"
 
+OLIVE_NAMESPACE_ENTER
+
 class TimeRuler : public SeekableWidget
 {
   Q_OBJECT
@@ -70,4 +72,6 @@ private:
 
 };
 
+OLIVE_NAMESPACE_EXIT
+
 #endif // TIMERULER_H