If Liquibase is on the classpath it will fire up on startup. Various
config options are available (as well as the option to disable it).
Liquibase uses a YAML format for changes (in classpath:db/changelog).
This commit adds auto-configuration and a starter,
spring-boot-starter-freemarker, for using FreeMarker view templates in
a web application.
A new abstraction, TemplateAvailabilityProvider, has been introduced.
This decouples ErrorMvcAutoConfiguration from the various view
technologies that Spring Boot now supports, allowing it to determine
when a custom error template is provided without knowing the details of
each view technology.
Closes#679
Update reference documentation to include a note explaining that
"blessed" versions a chosen based on the gradle plugin version, and
that builds are repeatable.
Fixes gh-619
