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/projecttoolbar/projecttoolbar.cpp

@@ -26,6 +26,8 @@
 
 #include "ui/icons/icons.h"
 
+OLIVE_NAMESPACE_ENTER
+
 ProjectToolbar::ProjectToolbar(QWidget *parent) :
   QWidget(parent)
 {
@@ -150,3 +152,5 @@ void ProjectToolbar::ViewButtonClicked()
     abort();
   }
 }
+
+OLIVE_NAMESPACE_EXIT