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

Commit adds:
* Implementation of PowerDNS as a provider
* Tests for said implementation
* github.com/ffledgling/pdns-go, which provides go client bindings for
  PowerDNS's HTTP API, as a dependency
* "pdns" as an additional option for the `--provider` flag
* `--pdns-server` and `--pdns-api-key` as additional flags for PowerDNS
  specific configuration

Add Foreign Cloud support to Azure Provider (#485)

* Add a flag that allows FQDN and Annotations to combine

Old behaviour is kept by default, a new flag is introduced to combine instead of overwrite

Fixes #218

* docs: add fqdn template combine to changelog

* for headless services use podip instead of hostip

* docs: add hostIP to podIP switch to changelog

* Support a comma separated list for the FQDN template

* Add documentation for comma separated FQDN templates

* chore: add multiple fqdn templates to changelog

digitalocean: Fix handling of domain record names

Update azure.md

Added nginx-ingress information and made setting up AzureDNS with k8s on AKS or other providers easier to understand.

Always build against latest stable version of golang

Fix typo for serviceAccountName in RBAC example

serviceAccountName was transposed onto the non-RBAC example

The DomainRecord response from the Digital Ocean API does not contain
the zone as part of the name and thus we must append the zone name when
converting it to an endpoint for the plan calculation.

Furthermore the root domain is identified by `@` and must be converted
to the zone name for the endpoint, and converted back to `@` when the
record is submitted to the DO API.

https://developers.digitalocean.com/documentation/v2/#retrieve-an-existing-domain-record

Fix #487

* Auto-detect google-project if provider is Google and no project is supplied.

* Add changelog entry.