This commit enables compatibility build against Spring Framework 5.
The Velocity and Guava support that are deprecated in the 1.x line have
been removed and few other classes contain minor change to comply to non
backward compatible changes in Spring Framework 5.
This commit also switches the required java version to 8.
Closes gh-6977
This commit updates the cache auto-configuration to provide a
`CouchbaseCacheManager` if a `Bucket` has been configured.
The global customizer infrastructure allows to further tune the cache
manager if necessary.
Closes gh-5176
Previously, native cache libraries were favored over a standard JSR-107
implementation. If a user has a working setup using JCache with one
provider and switch to another provider, his setup may be broken if we
happen to provide a native support for the new provider.
We now consistently favor JSR-107 if it is present. Native support can
still be enabled via the `spring.cache.type` property.
Closes gh-3822
Phillip Webb
Stephane Nicoll
John Blum
Spring Buildmaster
Eddú Meléndez