Add symmetric paths plot #20
Description
Add a button showing the opposite direction of the pair.
https://ps-dash.uc.ssl-hep.org/anomalous_paths/src_netsite=PIC-LHCOPNE&dest_netsite=JINR-T1-LHCOPNE
Example: on the page above, let users check src_netsite=JINR-T1-LHCOPNE & dest_netsite=PIC-LHCOPNE