Various fixes and improvements to Columns interface
Various fixes and improvements to Columns interface

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