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/toolbar/toolbar.h

@@ -27,6 +27,8 @@
 #include "widget/toolbar/toolbarbutton.h"
 #include "tool/tool.h"
 
+OLIVE_NAMESPACE_ENTER
+
 /**
  * @brief A widget containing buttons for all of Olive's application-wide tools.
  *
@@ -215,4 +217,6 @@ private slots:
 
 };
 
+OLIVE_NAMESPACE_EXIT
+
 #endif // TOOLBAR_H