SC F2F outcome: Attribute for XML behavior

[Yves Savourel <ysavourel@enlaso.com>]

During the face-to-face meeting there was a consensus on adding a new attribute indicating whether an original code may allow overlap (e.g. not behave like an XML element).
 
The attribute (which the name is not defined yet, but could possibly "mayOverlap" would exist in <sc>, <ec> and <pc>, allowing complete conversion in any direction while keeping all the information about the capability of the underlying original code.

The default for <pc> would be mayOverlap='no', and the default for <sc>/<ec> would be mayOverlap='yes'.

Remember that the attribute pertains to the original code, not to the XLIFF notation.

- tools can clue of this attribute to allow overlap or not
- this would allow us to drop 'transformed'

Any feedback welcome,
-ys