Added support for capturing virtualized traffic.
## VXLAN
https://en.wikipedia.org/wiki/Virtual_Extensible_LAN
VXLAN implemented as separate engine, which opens UDP socket and awaits traffic.
This approach is made to work with AWS Traffic Mirroring.
In order to enable VXLAN set `--input-raw-engine vxlan`
Example:
```
gor --input-raw :80 --input-raw-engine vxlan --output-stdout`
```
By default, it looks for vxlan traffic on the standard 4789 port, but you can override it with `--input-raw-vxlan-port`.
Additionally, you can allow only specific VNIs using `--input-raw-vxlan-vni`, or disallow by using the same option, but by adding "minus" sign to the value: `--input-raw-vxlan-vni -2`.
Example with all options:
```
gor --input-raw :80 --input-raw-engine vxlan --input-raw-vxlan-vni 1 --input-raw-vxlan-vni 2 --input-raw-vxlan-port 2222 --output-stdout
```
# VLAN
https://en.wikipedia.org/wiki/IEEE_802.1Q
VLAN protocol enabled using `--input-raw-vlan` argument, and you can filter for specific VLAN VIDs using `--input-raw-vlan-vid`. VLAN filtering happens on BPF level.
Example:
```
gor --input-raw :80 --input-raw-vlan --input-raw-vlan-vid 1 --output-stdout`
```
## Notes
Did a refactoring of RAW Input options, so it will be easy to extend in future.
