Add new wxTreeListCtrl class.

This is a facade for wxDataViewCtrl allowing to easily work with multi-column
trees, possibly with an optional checkbox in the first column. Its API is very
similar to wxTreeListCtrl and it provides a simple migration path from the
latter.

Add the class itself, documentation for it and minimal unit tests.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@68916 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/doxygen/mainpages/const_wxusedef.h

@@ -251,6 +251,7 @@ library:
 @itemdef{wxUSE_TOOLTIPS, Use wxToolTip class.}
 @itemdef{wxUSE_TREEBOOK, Use wxTreebook class.}
 @itemdef{wxUSE_TREECTRL, Use wxTreeCtrl class.}
+@itemdef{wxUSE_TREELISTCTRL, Use wxTreeListCtrl class.}
 @itemdef{wxUSE_TTM_WINDOWFROMPOINT, Obsolete, do not use.}
 @itemdef{wxUSE_URL, Use wxURL class.}
 @itemdef{wxUSE_URL_NATIVE, Use native support for some operations with wxURL.}