Allow Copy/paste inside DDF editor from DeConz-GUI

We all agree that the DDF editor included in Deconz-GUI is very handy.

However it is not possible by the GUI to include certain changes in the DDF (or the bugs of the current editor have side effects which sometimes prevent using it… see the requests already opened on the subject).

One way to make this easier for everyone would be to be able to copy/paste and not just preview the DDF directly in the editor.

Saving would only be allowed in the custom DDF directory specific to each operating system. Again this would avoid juggling sometimes to find where the right directory is located depending on the operating system (easier for the user and for the support as well)