Dockerize GATK. Scattering now works with containers. Tabix another docker image.

biopet/biopet.wdl

@@ -206,6 +206,8 @@ task ReorderGlobbedScatters {
     input {
         Array[File]+ scatters
         String scatterDir
+        # Should not be changed from the main pipeline. As it should not influence results.
+        String dockerTag = "3.6"
     }
 
     command <<<
@@ -226,6 +228,7 @@ task ReorderGlobbedScatters {
     }
 
     runtime {
+        docker: "python:" + dockerTag
         memory: 1
     }
 }