Added support for Sectioned View Plugin

Example:

```groovy
view(type: SectionedView) {
    name('project-summary')
    filterBuildQueue()
    filterExecutors()
    sections {
        listView {
            name('Project A')
            jobs {
                regex('project-A-.*')
            }
            columns {
                status()
                weather()
                name()
                lastSuccess()
                lastFailure()
            }
        }
        listView {
            name('Project B')
            jobs {
                regex('project-B-.*')
            }
            columns {
                status()
                weather()
                name()
                lastSuccess()
                lastFailure()
            }
        }
    }
}
```