Additional extensions for KeepNote organizer.

The package includes:
* Import Basket
Primitive import of Basket Notepad Databases.
* Import Folder Tree
Imports a folder tree as nodes in a notebook
* Import NoteCase
Primitive import of NoteCase .ncd Files
* Import Plain Text
Imports plain text files as nodes in a notebook
* Make File Catalog
Imports a folder tree, listing file names (maybe as links) notebook.