Added a merge classmethod to ViewGroup
Added a merge classmethod to ViewGroup

vascotenner/holoviews,ioam/holoviews,ioam/holoviews,mjabri/holoviews,mjabri/holoviews,ioam/holoviews,basnijholt/holoviews,mjabri/holoviews,basnijholt/holoviews,vascotenner/holoviews,vascotenner/holoviews,basnijholt/holoviews