Add support for creating groups by column-defined node lists

[AlexanderPico]

https://github.com/cytoscape/RCy3/blob/master/R/Groups.R#L95

Maybe a new function?

createGroupByColumn(group.name, column=NULL, value=NULL, 
                        network=NULL, base.url=.defaultBaseUrl) {
    net.suid <- getNetworkSuid(network,base.url)
    commandsPOST(paste0('group create groupName="',group.name,'"',
                                          ' nodeList="',column,'":"',value,'"',
                                          ' network="SUID:',net.suid,'"'),
                                 base.url = base.url)
}