Use 5G for minimum default vmem

public/biopet-framework/src/main/scala/nl/lumc/sasc/biopet/tools/FastqSync.scala

@@ -33,6 +33,8 @@ class FastqSync(val root: Configurable) extends BiopetJavaCommandLineFunction {
 
   javaMainClass = getClass.getName
 
+  override val defaultVmem: String = "5G"
+
   @Input(doc = "Original FASTQ file (read 1 or 2)", shortName = "r", required = true)
   var refFastq: File = null