Implement ip scp server enable support

[grotewortel]

Description
Can you please implement support for enabling scp server?

show running-config | i scp
This is part of the running config:

ip scp server enable

json path: .data["Cisco-IOS-XE-native:native"].ip.scp
This is the restconf-json formatted running config:

{
  "server": {
    "enable": [
      null
    ]
  }
}