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/projectexplorernavigation.cpp

@@ -26,6 +26,8 @@
 #include "common/define.h"
 #include "ui/icons/icons.h"
 
+OLIVE_NAMESPACE_ENTER
+
 ProjectExplorerNavigation::ProjectExplorerNavigation(QWidget *parent) :
   QWidget(parent)
 {
@@ -93,3 +95,5 @@ void ProjectExplorerNavigation::UpdateIcons()
   size_slider_->setMaximum(kProjectIconSizeMaximum);
   size_slider_->setValue(kProjectIconSizeDefault);
 }
+
+OLIVE_NAMESPACE_EXIT