Hidden text stable playground

From: !976 (comment 1997513)

About the tspan tips to hide text, I had no idea it was a possibility. Good to know it, I'll study how to use it in the credits to systematically hide comments/helpers to the transcript.

Well... Not if I do it first! You know...

I made myself a script for multiline text replace and now this script want to show some muscles.
Firstly I returned some hidden text removed from credits in 2cc5fa73 ( A and { )
This time it's properly hidden and won't show up in transcription.

Then, I tried to add something new and useful to (almost) all translations of EP13:

What I know so far with all the tests I made:

• <text> with 1 line is quite simple. You just have to remove <tspan> and make sure to move its style= to <text> (if it's not already there).

• I currently don't have a working method for <flow*>, so they have to be converted to <text>.

• Multiline <text> are more problematic. They can't be moved once encapsulated (new coordinates are changed on shell <text> and thus ignored). It can happen that position changes after encapsulation.

• Another problem with multiline <text> is legacy are legacy file versions. The safest way (I found) to prevent compression of lines is making every line as single line text and groupped with <g>. I can just say legacy = douleur the cool (sorry, I thougt it would be funny)