[FEATURE] Add overview MD file that lists all dataExtensions on one page / CSCLSROZ-449

[JoernBerkefeld]

idea is to show what dataExtensions exist, what folders they are in (or if they are hidden due to missing folders), how many rows of data they contain and others statistics (last change, by whom, bla bla).

each should then have a link to the already existing detailed md file that shows the data structure.

once we got "recover dataExtension " built, we could offer a "copy command" option here as well. 

similarly one for "delete dataExtension "