All ancestors must be active to unarchive a project.
Show the entire projects tree on admin project list.
Makes Project.allowed_to_condition actually works with nested sets.
Replaces #active_children with nested scopes #descendants.active
Removes calls to child_ids.
Makes parent parent assignment work on project form.
Use acts_as_nested_set instead of acts_as_tree for project hierarchy.
Adds a branch for unlimited project hierarchy.
CHANGELOG updated.
Merged r2109, r2118, r2130, r2131, r2134, r2135, r2136 and r2139 to r2145 from trunk.
