Add Groovy crawl configs

[ato]

This enables crawl configuration files to use Spring's Groovy Bean Definition DSL as an optional alternative to Spring XML. It uses the same bean configuration model but the syntax is more terse and human-readable. No more need for & in seed URLs. :-)

   checkpointService(CheckpointService) {
        checkpointIntervalMinutes = 15
        checkpointsDir = 'checkpoints'
        forgetAllButLatest = true
   }

It also enables some powerful scripting capabilities. For example, defining a custom DecideRule directly in the crawl scope without needing ScriptedDecideRule:

scope(DecideRuleSequence) {
    rules = [
        new RejectDecideRule(),
        // ACCEPT everything linked from a .pdf file
        new PredicatedDecideRule() {
             boolean evaluate(CrawlURI uri) {
                 return uri.via?.path?.endsWith(".pdf")
             }
        },
        // ...
    ]
}

The main downsides are defining nested inner beans can be a bit awkward, some of the errors can be cryptic, and you can't just manipulate the config files with an XML parser.

This commit includes a Groovy version of the default crawl profile for reference, but doesn't expose a way to use it in the UI yet. For now, you need to manually create a crawler-beans.groovy file in your job directory.