Several changes:

    - fix setFirstFocus typo (#2870)
    - fix bootstrap WNavigationBar responsive problems (#2813)
    - fix cn, ru homepage (#2866)
    - added a WSortFilterProxyModel::invalidate() method
    - make WTemplate resilient against widgets being removed during rendering
    - remove C++11 constexpr idea for WFormModel fields (#2852)
    - patch from Bruce: do not parse 'f' and 't' values as an exception (#2841)