Throttles the executions

BlockingExecutor.scala

package core

import java.util.concurrent.ArrayBlockingQueue

class BlockingExecutor(maxParallelism: Int) extends SBLogger{
	
	private case object Execution
	private val queue = new ArrayBlockingQueue[Execution.type](maxParallelism)
	
	def execute[T](execution: => T): T = {
		queue.put(Execution)
		val res = try {
			execution
		} finally {
			queue.poll()
		}
		res
	}
}