Migrate to groovy templates from Spring 4.1

Update `GroovyTemplateAutoConfiguration` to use Spring 4.1 Groovy
Markup Template infrastructure instead of Boot's.

Fixes gh-1552
Trim some fat from groovy templates

The old resolver class is deprecated already, and there's no reason
to continue to support the View and View resolver implementations
from Boot 1.1, so I removed those. Also there is no need to support
older versions of Groovy, so I removed a config class that was
conditional on a groovy version (by looking for the markup support).

Fixes gh-1578