replace grouped filter with multigroup channel filters

[wenqiang-gu]

Implement the multigroup channel filters as discussed in #327

To maintain backwards compatibility, the "grouped_filter" interface is kept. Here is an example to use the new interface in the configuration:

type: 'OmnibusNoiseFilter',
data: {

  grouped_filter: [ ] // keep empty for backwards compatibility
                     // need to assign empty array explicitly otherwise "mbCoherentNoiseSub" filter
                      // would be used: cfg["grouped_filters"][0] = "mbCoherentNoiseSub"; 

  multigroup_coherent: [
    // The order of execution is important
    {
      channelgroups: chndb.data.femb_groups;
      filters: [wc.tn(filter1), … ]
     },

    {
      channelgroups: chndb.data.groups; // coherent channel groups
      filters: [wc.tn(filter2), … ]
     },

  ],
}, 

[wenqiang-gu]

Here, I add a sanity check for the PDHD data after running coherent noise filters with different configuration:

[HaiwangYu]

Compiles and the SigProc results look identical with 0.27.1