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/node/dependency.cpp

@@ -22,6 +22,8 @@
 
 #include "node.h"
 
+OLIVE_NAMESPACE_ENTER
+
 NodeDependency::NodeDependency() :
   node_(nullptr)
 {
@@ -58,3 +60,5 @@ const TimeRange &NodeDependency::range() const
 {
   return range_;
 }
+
+OLIVE_NAMESPACE_EXIT