Import KAddressbookImportExport library from kdepim-apps-libs

This library provides an interface to implement import/export plugins for KAddressbook. It was agreed that it is OK for applications to install their own plugin interface libraries, so moving the library from kdepim-apps-libs gets us one step closer to killing that repo.

As part of the move I renamed files and classes and removed KAddressbookImportExport from the name, since they are already in KAddressbookImportExport namespace (which required adjusting existing code in KAB.

The library has been also moved from KF5 to KPim namespace, since this library is never going to become a Framework.