remove atob/btoa from database stored sheets
As the sheets stored in encoded form in the database are getting pretty large (up to several MB of text!!!) it would reduce the size of the database and the amount of data that has to be handled a lot if the sheets are stored in their html form instead of encoded.
write a script that converts the stored sheets from encoded to decoded state.
add decoding when a sheet is saved.
add encoding when a sheet is loaded and sent to the client.
execute the transformation script on the server to convert all stored sheets.
fix with https://gitlab.dirk-benkert.de/shadowrun/gearbox/issues/20