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/projectexplorer/projectexplorer.h

@@ -33,6 +33,8 @@
 #include "widget/projectexplorer/projectexplorernavigation.h"
 #include "widget/projecttoolbar/projecttoolbar.h"
 
+OLIVE_NAMESPACE_ENTER
+
 /**
  * @brief A widget for browsing through a Project structure.
  *
@@ -163,4 +165,6 @@ private slots:
 
 };
 
+OLIVE_NAMESPACE_EXIT
+
 #endif // PROJECTEXPLORER_H