Add AWS Service Discovery provider

[Cloudflare] Custom record TTL

Signed-off-by: Nick Jüttner <nick@juni.io>

Signed-off-by: Nick Jüttner <nick@juni.io>

* Minor changes to docs and faq

* Other minor changes

* better docs

* Addressed comments

* Add new connector source

* Update docs for connector source

* use ticker

* stop the ticker

* add support for hostname annotation in ingress resource

* implement getHostnamesFromAnnotations and use that in ingress/service

* source/service: if clusterIP: None, set TTL

* source/service: test headless endpoints with TTL

docs/tutorials: add pods resources to external-dns ClusterRole

* fix(google): correctly filter records that don't match all filters

* update changelog with the filters fix

* fix(google): add test to ensure domain filter works

Fixed Bug in PowerDNS provider and added testcases

* Fixed PowerDNS provider bug affecting endpoint conversion to
  zone in a particular case
* Added a regressive test case, covered an additional case

PowerDNS provider bug: In the function ConvertEndpointsToZones,
the endpoints are sorted lexicographically increasing
(and by record type in case of match). The zones are sorted by
decreasing order of length. There's a loop through of zones
under which the code loops through endpoints. In the case
the first endpoint does not match with the first zone,
the complete zone won't get populated with any endpoints.

AWS: add support for AWS Network Load Balancers

AWS: Allow to assume another role

Inititial support for multiple targets per record

Add docs for pdns provider

RBAC permissions

Add PDNS as a Provider