Prior to this commit, custom `ProtocolResolvers` set on the
`ApplicationContext` were lost when Devtools is used as the customized
`ResourceLoader` did not copy any customization made to the default
resource loader.

This commit makes sure to copy any `ProtocolResolver` set on the context.

Closes gh-9331

Closes gh-9054

Closes gh-9360

Closes gh-9410

Closes gh-8927

* pr/9411:
  Polish contribution
  Ensure `QuartzDatabaseInitializer` is initialized before `Scheduler`

Closes gh-9411

If the auto-configured `Scheduler` instance backed by JDBC job store is
used as a dependency in an application component, the initialization of
`Scheduler` will be triggered before `QuartzDatabaseInitializer`. This
will result in failure due to schema not being prepared in time for
`Scheduler` to populate job details.

This commit ensures `QuartzDatabaseInitializer` is initialized before the
auto-configured `Scheduler` by introducing a dependency between the two.

See gh-9411

Closes gh-9407
Closes gh-9135

* pr/9404:
  Polish "Document InfluxDB support"
  Document InfluxDB support

Closes gh-9404

See gh-9404

This commit removes the `client` namespace for InfluxDB as the
component that is created is `InfluxDB`, not `InfluxDBClient` or
something.

This aligns with all the other url/user/password properties Spring
Boot provides already

See gh-9066

Different versions of Docker produce different responses when building
and tagging an image. On CI, a response with a stream like
"Successfully built 185991ffe24a" followed by a response with a
stream like "Successfully tagged spring-boot-it/centos:6.9-a23bced6"
is received. By default, for the building of an image to be considered
successful, the Docker Java client requires the stream for the last
response item to contain "Successfully built". This means that, on the
CI server, it incorrectly believes that the building of the tagged
image has failed.

This commit uses a custom BuildImageResultCallback that doesn't
require the last response to be the one that has a stream containing
"Successfully built". Instead, it looks back through the error-free
responses (newest to oldest) looking for one with a stream containing
"Successfully built".

See gh-6299

CentOS 5 was declared EOL in March 2017 and yum on longer works
out of the box. 6.9 is the latest release of CentOS 6. Tests for
CentOS 7 have not been added as it uses systemd rather than SysVinit.

Closes gh-9395