Organize views as tree - Githubissues

New features according to CHANGELOG

changed appearance from tabular view to tree view
added 'directory' elements to organize and manage groups of views
added drag'n drop feature allowing to relocate views or directories to another branch in the tree
added column for view ID
added functions to Python GUI API to create, modify and delete views and directories
added UNDO functionality for create/delete view and directory actions
fixed sort-by-column feature. The tree is not sorted at program start thus showing elements in 'natural' order.

emsec / hal