First thorough implementation. Provides three modes:
1) a flat list. Images are sorted by depth first search,
in which edges are accessed modification date time order
2) a simple tree. Same order as above, but with added depth.
3) A combined view with FilterActions available. Uses longestPath
to get a main path. After the current item is reached on the path,
all leaf images (current versions) are listed flat,
with intermediates below a subitem (currently effectively hidden)