In preparation of a larger merge request which adds more ways on
source matching the variables indicating a host match are renamed to the
more generic term source.

In case of a proxy request the headers are hidden for the client calling
the proxy.

In case of the redirect the headers are added before sending the
redirect response back to the client.

It is now possible to add a ttl setting in seconds to the settings of a
route which will set a redis EXPIRE tag on the respective route.

The default is persistent.

The proxy now first tries to find a matching route based on the host and
if this does not yield a result it will next try to find a route based
on the request_uri (without leading slash).

This commit depends on the presence of feature/headers.

In newer versions or some environments it may occur that the responder
API complains about a missing, explicit default route key.

When using redis EXPIRE or any other automated cleaning utility it may
happen that a hash is not fully removed. If a new hash is set at the
same key and there are null values the old stored values may be reused.