In order to do a relaease not waiting for Spring Cloud
Finchley.REALEASE move all depedent stuff into a seperate module which
can be excluded during build

This makes sure that the headers are written to the output stream
before the async dispatch. Otherwise we end up with strange NPEs
when flushing the buffer on writing the body.

fixes #715

..to gain more performance and reduce gc pressure

fixes #713

closes #713

Fixes stalls in threaddump view due to not completing responses - only
reactive applications were affected so far.

If the build version of the instance is present in the metadata it's now
also considered and the version is now a attribute on the instance
itself. So when using non-boot application they can provide it via the
registration metadata.

- use MimeMessage with Content-Type text/hmtl
- use a single template for subject and body
- use a Spring aware TemplateResolver

The WebClient's responses should be always consumed, so that underlying
buffers are released.

Fixes #666

This commit enables client and server to work out of the box on
CloudFoundry.
The client derives the registration info (url and metadata) from the
VCAP environment variables.
The server computes a unique instanceId and the correct headers for the
cf router based on the metadata provided by instances. Also suppots the
CloudFoundry discovery client ootb.

closes #434

... to support multiple HttpHeadersProviders

fixes #647

closes #560