ETree cleanups.
Remove e_tree_selected_row_foreach().

Reducing API bloat.  Do this instead:

  selection = (ESelectionModel *) e_tree_get_selection_model (tree);
  e_selection_model_foreach (selection, callback, closure);
Remove e_tree_selected_path_foreach().

Reducing API bloat.  Do this instead:

  selection = (ETreeSelectionModel *) e_tree_get_selection_model (tree);
  e_tree_selection_model_foreach (selection, callback, closure);
Remove e_tree_drag_dest_set().

Reducing API bloat.  Call gtk_drag_dest_set() directly instead.
Remove unused e_tree_drag_dest_set_proxy().

It just calls gtk_drag_dest_set_proxy() anyway.
Remove unused e_tree_drag_dest_unset().

It just calls gtk_drag_dest_unset() anyway.
Remove unused e_tree_drag_get_data().

It just calls gtk_drag_get_data() anyway.
Remove unused e_tree_drag_highlight().
Remove unused e_tree_drag_unhighlight().
Remove unused e_tree_right_click_up().
Remove e_tree_node_is_expanded().

Reducing API bloat.  Do this instead:

  adapter = e_tree_get_table_adapter (tree);
  expanded = e_tree_table_adapter_node_is_expanded (adapter, path);
Remove e_tree_node_set_expanded().

Reducing API bloat.  Do this instead:

  adapter = e_tree_get_table_adapter (tree);
  e_tree_table_adapter_node_set_expanded (adapter, path, expanded);
Remove e_tree_node_set_expanded_recurse().

Reducing API bloat.  Do this instead:

  adapter = e_tree_get_table_adapter (tree);
  e_tree_table_adapter_node_set_expanded_recurse (adapter, path, expanded);
Remove e_tree_root_node_set_visible().

Reducing API bloat.  Do this instead:

  adapter = e_tree_get_table_adapter (tree);
  e_tree_table_adapter_root_node_set_visible (adapter, visible);
Remove e_tree_node_at_row().

Reducing API bloat.  Do this instead:

  adapter = e_tree_get_table_adapter (tree);
  path = e_tree_table_adapter_node_at_row (adapter, row);
Remove e_tree_row_of_node().

Reducing API bloat.  Do this instead:

  adapter = e_tree_get_table_adapter (tree);
  row = e_tree_table_adapter_row_of_node (adapter, path);
Remove e_tree_root_node_is_visible().

Reducing API bloat.  Do this instead:

  adapter = e_tree_get_table_adapter (tree);
  visible = e_tree_table_adapter_root_node_is_visible (adapter);
Remove e_tree_show_node().

Reducing API bloat.  Do this instead:

  adapter = e_tree_get_table_adapter (tree);
  e_tree_table_adapter_show_node (adapter, path);
Remove e_tree_save_expanded_state().

Reducing API bloat.  Do this instead:

  adapter = e_tree_get_table_adapter (tree);
  e_tree_table_adapter_save_expanded_state (adapter, filename);
Remove e_tree_load_expanded_state().

Reducing API bloat.  Do this instead:

  adapter = e_tree_get_table_adapter (tree);
  e_tree_table_adapter_load_expanded_state (adapter, filename);