Add Parse Ethernet frame Operation, allow Parse IPv4 Header to cascade

[Kalkran]

This adds a new operation+tests that parses Ethernet frames.
Recently, I've been provided with Base64-encoded single packets which are annoying to decode manually, or even to strip the Ethernet header off.
This operation adds a basic information output and a 'packet data'-only which allows cascading to other Networking-related parsers (ie IPv4). I am still playing with the idea of updating those to allow the return of encapsulated data as well - allowing a quick/basic packet analysis through a recipe.

[Kalkran]

An accidental push before switching branches broke UI tests. These are now fixed.
The last few commits also allow the pre-existing "Parse IPv4 Header" to cascade its data down the line instead of only presenting a HTML table. Together with the Ethernet frame operation and the other IP-related parsers this allows analysis and decoding of IP packets (for example as logged by Suricata) and their contents.