Update to digikam 5.2.0

- Updated migration_from_digikam4.diff to migrate also the
geobookmarks.xml file from digikam4. This patch thus fixes
kde#364258, kde#357944 and kde#368968.

- Added migration_from_digikam4.diff to support migration of
settings and database from digikam4 the first time digikam5
is run by adding a migration page in the welcome wizard and
letting the user choose what to do (kde#364258).

- Workaround kde#369517 by removing libvkontakte translations
(not built but installed anyway)

- Ensure akonadi-contact-devel is not pulled in for ppc64, as
QWebEngine is not available for that platform

- Don't disable building the documentation any more, kde#365135 is
fixed in 5.2.0

- Update to Digikam v5.2.0: https://www.digikam.org/node/758
* many bugfixes
* updated documentation
- Remove build-32bits.patch again, fixed upstream
- Add threadweaver and gphoto buildrequires
- Enable appstyles to not force fusion style
- Fix miscellaneous rpmlint warnings

- Add find_libastro-qt5.patch to fix build of geolocation support
in Leap 42.1

- Update to Digikam v5.1.0: https://www.digikam.org/node/756