XR selection routines

[phockett]

Some selection routines broken in XR 2022.3.0 (and presumably more recent versions...?).

Issue seems to be with slicing on float indexes, produces key or type errors, but used to work.

For example, slicing ADMs by t-index:

   # And for the ADMs...
    # SLICE version - was working, but not working July 2022, not sure if it's data types or Xarray version issue? Just get KeyErrors on slice.
    # data.selOpts['ADM'] = {}   #{'thres': 0.01, 'inds': {'Type':'L', 'Eke':1.1}}
    # data.setSubset(dataKey = 'ADM', dataType = 'ADM', sliceParams = {'t':[38, 44, 4]}) 

    #********** HACKS/DEBUG
    # Inds/mask version - seems more robust?
    # trange=[38, 44]  # Set range in ps for calc
    # tStep=4  # Set tStep for downsampling
    # tMask = (data.data['ADM']['ADM'].t>trange[0]) & (data.data['ADM']['ADM'].t<trange[1])
    # data.data[data.subKey]['ADM'] = data.data['ADM']['ADM'][:,tMask][:,::tStep]  # Set and update
    # print(f"ADMs: Selecting {data.data['subset']['ADM'].t.size} points from {data.data['ADM']['ADM'].t.size}")