Removed the extern files, except the JSON file with the node descriptions, this will be loaded in offline mode too.

- fixed: clear selected nodes, works with several or all selected nodes (reason: two counting variables with the same name "i" where used in two nested loops)
- new: change node names (you can assign names to the nodes, these will be used as IDs if exported or re-imported to CPP (Arduino code)
- fixed: import merges imported nodes to existings ones, skipping nodes with the same name
- fixed: tooltips are now working, extracting the first paragraph of the HTML code
- new: nodes definition extracted to JSON file
- new: nodes help pages extracted to single HTML files
- new: form pages extracted to single HTML files
- new: asynchronous loading of JSON, help and form data, data will only be loaded when needed
- style: adapted the size of the palette, labels had been partially hidden