Testing toolbox love

[eugeneia]

This PR hijacks #708 and #690 with permission from @petebristow. In short it imports his Testsink app as apps.test.match.Match and uses this app to simplify some replay-type selftest throughout the code base including the selftests for: apps.test.match (see #727), apps.keyed_ipv6_tunnel.tunnel, apps.socket.raw and apps.tap.tap. Other minor changes include:

• Changed documentation of Source app to reflect configuration and specify zeroed packet data
• Document apps.test.synth and fix it to generate proper Ethernet LLC packets
• Introduce modest option for apps.test.match for “match at least some”-style tests

[lukego]

Upstream needed - @kbara or @wingo?

[kbara]

LGTM, thank you.
@lukego : what's the process for merging this, given that the PR is not based against kbara-next - a new PR, or manual merging to kbara-next and closing this?

[eugeneia]

@kbara I do the following (my upstream remote is called “snabbco”:

1=<PRNUMBER>
git fetch snabbco pull/$1/head:pr$1
git merge --no-ff --edit -m "Merge PR #$1 () into $(git rev-parse --abbrev-ref HEAD)" pr$1
git branch -D pr$1

I have the following git aliases in my ~/.gitconfig that make life easy:

[alias]
        pr = "!pr() { git fetch snabbco pull/$1/head:pr$1; }; pr"
        merge-pr = "!merge_pr() { git merge --no-ff --edit -m \"Merge PR #$1 () into $(git rev-parse --abbrev-ref HEAD)\" pr$1 && git branch -D pr$1; }; merge_pr"