Added 42 unit tests of util.sanitize_identifier and util.allowable
Added 42 unit tests of util.sanitize_identifier and util.allowable

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