Add pipe element masking

[Wazzaps]

This means I can disable parts of the pipeline (from the end to the start) to debug each piece. If I start with: [ .[] | {(.ifname): .address} ] | add | .eth0 Then I should be able to switch to (with e.g shortcut: Shift+Left): [ .[] | {(.ifname): .address} ] | add ~~| .eth0~~ And then: [ .[] | {(.ifname): .address} ] ~~| add | .eth0~~ And then: [ .[] ~~| {(.ifname): .address}~~ ] ~~| add | .eth0~~