fixes #789

Before this, the route was always lower-cased, but this makes the route registered with Spring Boot Admin not accessible. This changes to use the route as it is, and updates a test to include an uppercase letter in the route.

fixes #738

The TaskScheduler used for periodically registering is removed from the
application context and moved to the ApplicationRegistrationListener.

see #478

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

in order to easily contribute programmatically to the metadata this
commit adds an MetadataContributor as extionsion point.

...otherwise it won't play nice with the bootstrap context

This removes the spring-boot-starter-parent from the build, and
duplicates the necessary plugin configuration in he Spring Boot Admin'
parent instead. This way our BOM doesn't include version for
dependencies managed by boot's BOM