Enhancement request: show differences between two dat files

[Richard Elkins]

Two processes in succession:

1. For each entry in dat file dat1, look for a match in dat file dat2.
2. For each entry in dat file dat2, look for a match in dat file dat1.

The comparison between dataframe entries uses the following dataframe columns:

• Coarse channel number (exact match)
• Frequency (within rtol) where rtol is the {math,numpy}.isclose() value (E.g. 0.0001 which signifies 0.01%)
• Drift rate (within rtol)

[Richard Elkins]

Release 2.3.0