When encoding big blobs of data in base64, insert newlines.
Base64 allows it, CSS allows it, so not need to make GtkTextView
struggle with multi-megabyte lines.
Update nodeparser tests to reflect this change.
If somebody does a transform like
scale(5) scale(10) translate(1,1) translate(5,0)
store it instead as
scale(50) translate(6,1)
This way, less memory is consumed and transforms are easier to read.
In particular, this simplifies the typical transforms we do in GTK,
which are just one translation after another.
