* gh-1826:
  Add Liquibase rollback file support

Add a `liquibase.rollback-file` property which can be used to write
a rollback file when migrations occur.

Fixes gh-1826
Closes gh-5535

Add a sample showing how Hibernate 4 can be used if necessary.

See gh-2763

Upgrade to Hibernate 5.1, whilst still retaining compatibility with
Hibernate 4.3. This commit introduces the following changes:

* Add SpringPhysicalNamingStrategy to provides lowercase/underscore
  table names support. This should be equivalent to the previous
  SpringNamingStrategy that was used with Hibernate 4. No
  ImplicitNamingStrategy is provided since the Hibernate 5 defaults
  appear to be roughly equivalent to the conventions used in Spring
  Boot 1.3
  spring.jpa.hibernate.naming.

* Migrate  `spring.jpa.hibernate.naming-strategy` to
  `spring.jpa.hibernate.naming.strategy` and provide additional
  properties for physical and implicit.

* Add `spring.jpa.hibernate.use-new-id-generator-mappings` property and
  default to `false` when on Hibernate 5 to retain back compatibility.

See gh-2763

Previously, we only had dependency management for
selenium-htmlunit-driver. It depends on three other Selenium modules
for which dependency management was not provided. This means that there
was a risk that a mixture of versions would end up on the classpath.

This commit adds dependency management for the Selenium modules upon
which selenium-htmlunit-driver depends.

Closes gh-5520

Closes gh-5444

While the benign exception that Gemfire outputs is unfortunate, it
isn't sufficient justification for adding dependency management for
Spring Shell.

Closes gh-5444

Previously, JarLauncher considered any entry whose name began with
BOOT-INF/classes/ as being a nested entry. This was incorrect as it
meant that subdirectories of BOOT-INF/classes/ would be added to the
classpath rather than just BOOT-INF/classes/ itself.

This commit updates JarLauncher so that only directory entries with a
name equal to BOOT-INF/classes are used.

Closes gh-5610

Previously, if a JarFile was created from a directory nested inside
another jar file, it would look for the manifest in
pathFromRoot/META-INF/MANIFEST.MF. This is incorrect as, unlike a
JarFile created from a jar file, the archives are one and the same
so the manifests should be too.

This commit updates JarFile so that its aware of how it was created
(direct from a file, from a nested directory, from a nested jar). If
it was created from a file or from a nested jar, it uses its manifest.
If it was created from a nested directory, it uses the manifest of the
root archive.

Closes gh-5609

Closes gh-5608

Closes gh-5607

Closes gh-5606

Closes gh-5605

Closes gh-5604

Closes gh-5603

Closes gh-5602

Closes gh-5601

Closes gh-5600

Closes gh-5599

Closes gh-5598

Closes gh-5597

Closes gh-5596

Closes gh-5595

Closes gh-5594

Closes gh-5593

Closes gh-5592

* pr/5561:
  Polish contribution
  Fix spring.profiles.active value handling

Closes gh-5561

Previously, `spring.profiles.active` did not trim the individual comma
separate values. As a result, such profile wasn't enabled as expected.

This commit makes sure to trim whitespaces.

Closes gh-5442

Closes gh-3945

Closes gh-5588

Closes gh-5587

Closes gh-5586

Closes gh-5585

Closes gh-5584

Closes gh-5583

Closes gh-5582

Closes gh-5581