Add 1.7.0 notes already (#3779)

* Add 1.7.0 notes already

This is the work-in-progress release notes for 1.7.0, adding it now so
we can craft it will we work towards 1.7.0.

Notes currently yell that 1.7.0 is backwards incompatible.
Signed-off-by: Miek Gieben <miek@miek.nl>

* Update notes/coredns-1.7.0.md
Co-Authored-By: Ben Kochie <superq@gmail.com>
Co-authored-by: Ben Kochie <superq@gmail.com>

notes/coredns-1.7.0.md

++++
+title = "CoreDNS-1.7.0 Release"
+description = "CoreDNS-1.7.0 Release Notes."
+tags = ["Release", "1.7.0", "Notes"]
+release = "1.7.0"
+date = 2020-03-24T10:00:00+00:00
+author = "coredns"
++++
+
+The CoreDNS team has released
+[CoreDNS-1.7.0](https://github.com/coredns/coredns/releases/tag/v1.7.0).
+
+This is a **backwards incompatible release**. Major changes include:
+* Better metrics names (PR #3776)
+* New `transfer` plugin that removes the need for plugins to perform their own zone transfers.
+added `transfer` plugin that removes the need for plugins to perform their own zone transfers.
+
+As this was already backwards incompatible release, we took the liberty to stuff is much of it in
+one release as possible to minimize the disruption going forward.
+
+## Brought to You By
+## Noteworthy Changes