Introduce config var for moved-paragraph-detection threshold

Introduce config var for moved-paragraph-detection threshold

This introduces a configuration variable for the bailout threshold for
the moved-paragraph-detection in wikidiff2.
This allows to rollout a new version of wikidiff2 that supports
detecting changes in moved paragraphs without changing behaviour of all
wikis in production as the default value of the setting (0) will leave the
new feature disabled.
Compatibility with older versions of wikidiff2 is retained by checking for
the version number of wikidiff2 and calling the method without the 4th
parameter if the version is < 0.3.0.

Bug: T166571
Change-Id: Ic01054354a4fbba410e58c9873edcbde797f883d