[VersionConverter] How to deal with Section.include

[mpsonntag]

How to handle Section.include conversion from 1.0 to 1.1.

Analogous to #216.

[mpsonntag]

By default, a conversion that encounters a non-v1.1 odml Section.include will lead to a [warning] conversion log message, but will export the Section.include unchanged.
The converter will include a flag that enables to pull in the included Section from the link, adds it to the document, converts the pulled in Section to v1.1 as well and removes the Section.include from the resulting v1.1 file.