Allow dependency management to be applied to specific configurations

In addition to  global dependency management that applies to every
configuration, the plugin now also allows configuration-specific
dependency management to be declared. If the both the global dependency
management and the configuration-specific dependency management
provide dependency management for a dependency, the
configuration-specific dependency management takes precedence.

Single configuration:

project.dependencyManagement {
     compile {
          dependencies {
               …
          }
          imports {
               …
          }
     }
}

Multiple configurations:

project.dependencyManagement {
     configurations(compile, custom) {
          dependencies {
               …
          }
          imports {
               …
          }
     }
}