Automatically add frames for elements with a description tag (<desc>) "sozi" or "sozi:Title"

Adds a frame for every element with a description tag "sozi".
- If element is a rect, hide is set to true
- If sozi description tag has a title added, this is used
- If no title is given and element is a text field, use collected content of all tspan elements as title.

In the svg the desc-tags look like this:
<desc id="desc10592">sozi</desc>
or
<desc id="desc10593">sozi: This is the title of the new frame</desc>