Revert "Remove node levels; redefine node types; misc"

This reverts commit 95ba52ad09f9094ee30210c89aa1a7f114e424d1.

Conflicts:
	svir/globals.py
	svir/resources/js/svir_viewer_d3_tree.js
	svir/resources_rc.py
	svir/weight_data_dialog.py
better bahaviour, all dialogs now work correctly