engine: Make link report prettier
engine: Make link report prettier

The standard link report printout is now a little prettier: links are
alphabetically sorted (resolves #385), punctuation is improved, and
values are printed with commas and justified.

Before:

    link report
    597223954 sent on Virtio_A.tx -> NIC_A.rx (loss rate: 0%))
    137411842 sent on NIC_A.tx -> Virtio_A.rx (loss rate: 0%))
    597223786 sent on NIC_B.tx -> Virtio_B.rx (loss rate: 0%))
    137411851 sent on Virtio_B.tx -> NIC_B.rx (loss rate: 0%))

After:

    link report:
	      17,747,602 sent on NIC_A.tx -> Virtio_A.rx (loss rate: 0%)
	      70,955,552 sent on NIC_B.tx -> Virtio_B.rx (loss rate: 0%)
	      70,955,729 sent on Virtio_A.tx -> NIC_A.rx (loss rate: 0%)
	      17,747,621 sent on Virtio_B.tx -> NIC_B.rx (loss rate: 0%)

snabbnfv-goodies/snabbswitch,wingo/snabbswitch,alexandergall/snabbswitch,dwdm/snabbswitch,snabbco/snabb,lukego/snabbswitch,pavel-odintsov/snabbswitch,Igalia/snabb,heryii/snabb,eugeneia/snabb,dpino/snabbswitch,aperezdc/snabbswitch,alexandergall/snabbswitch,wingo/snabb,plajjan/snabbswitch,SnabbCo/snabbswitch,mixflowtech/logsensor,Igalia/snabb,wingo/snabb,pirate/snabbswitch,SnabbCo/snabbswitch,wingo/snabb,andywingo/snabbswitch,fhanik/snabbswitch,SnabbCo/snabbswitch,mixflowtech/logsensor,snabbnfv-goodies/snabbswitch,kellabyte/snabbswitch,Igalia/snabb,pirate/snabbswitch,Igalia/snabb,alexandergall/snabbswitch,lukego/snabb,dpino/snabb,kbara/snabb,justincormack/snabbswitch,heryii/snabb,mixflowtech/logsensor,lukego/snabbswitch,pirate/snabbswitch,snabbco/snabb,mixflowtech/logsensor,aperezdc/snabbswitch,hb9cwp/snabbswitch,javierguerragiraldez/snabbswitch,kellabyte/snabbswitch,plajjan/snabbswitch,mixflowtech/logsensor,virtualopensystems/snabbswitch,fhanik/snabbswitch,pavel-odintsov/snabbswitch,Igalia/snabb,snabbco/snabb,pavel-odintsov/snabbswitch,javierguerragiraldez/snabbswitch,hb9cwp/snabbswitch,eugeneia/snabb,snabbco/snabb,snabbnfv-goodies/snabbswitch,SnabbCo/snabbswitch,eugeneia/snabbswitch,dpino/snabb,plajjan/snabbswitch,eugeneia/snabb,aperezdc/snabbswitch,Igalia/snabbswitch,eugeneia/snabb,heryii/snabb,hb9cwp/snabbswitch,heryii/snabb,justincormack/snabbswitch,lukego/snabbswitch,dpino/snabb,andywingo/snabbswitch,kbara/snabb,xdel/snabbswitch,virtualopensystems/snabbswitch,alexandergall/snabbswitch,eugeneia/snabb,xdel/snabbswitch,dpino/snabb,snabbco/snabb,lukego/snabbswitch,heryii/snabb,snabbco/snabb,lukego/snabb,wingo/snabb,kbara/snabb,wingo/snabbswitch,eugeneia/snabbswitch,andywingo/snabbswitch,eugeneia/snabb,kellabyte/snabbswitch,wingo/snabbswitch,Igalia/snabbswitch,Igalia/snabb,justincormack/snabbswitch,lukego/snabb,eugeneia/snabbswitch,eugeneia/snabb,eugeneia/snabbswitch,kbara/snabb,Igalia/snabbswitch,hb9cwp/snabbswitch,heryii/snabb,snabbco/snabb,snabbnfv-goodies/snabbswitch,eugeneia/snabb,fhanik/snabbswitch,justincormack/snabbswitch,plajjan/snabbswitch,dpino/snabb,xdel/snabbswitch,Igalia/snabb,javierguerragiraldez/snabbswitch,alexandergall/snabbswitch,alexandergall/snabbswitch,wingo/snabb,Igalia/snabb,Igalia/snabbswitch,snabbco/snabb,dpino/snabb,alexandergall/snabbswitch,dwdm/snabbswitch,virtualopensystems/snabbswitch,andywingo/snabbswitch,dpino/snabbswitch,Igalia/snabbswitch,aperezdc/snabbswitch,dwdm/snabbswitch,wingo/snabb,wingo/snabbswitch,dpino/snabbswitch,alexandergall/snabbswitch,kbara/snabb,kbara/snabb,dpino/snabb,lukego/snabb,dpino/snabbswitch