feat: set the default memory unit type to megabytes

This makes it easier to support all schedulers out of the box - all other schedulers assume megabytes when no unit is specified.

tests/unit/resource_1.bats

@@ -51,6 +51,18 @@ teardown() {
   echo "status: $status"
   assert_output "536870912"
 
+  run /bin/bash -c "dokku resource:limit --memory 512 $TEST_APP"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+
+  dokku ps:rebuild "$TEST_APP"
+  CID=$(< $DOKKU_ROOT/$TEST_APP/CONTAINER.web.1)
+  run /bin/bash -c "docker inspect --format '{{.HostConfig.Memory}}' $CID"
+  echo "output: $output"
+  echo "status: $status"
+  assert_output "536870912"
+
   run /bin/bash -c "dokku resource:limit --memory 1024MB --process-type worker $TEST_APP"
   echo "output: $output"
   echo "status: $status"