Migrate grc blocks from xml to yaml

Convert the blocks using cmdline_converter.py script from
https://gist.githubusercontent.com/haakov/4228ff6a14486641add538483093e86b/raw/c861a840e31182ace2e74f5425e356cb4f8b183a/cmdline_converter.py

Change-Id: Iee5c611a2e100bd2fdf487611a867dc937d8c292
diff --git a/grc/misc_utils/gsm_message_file_source.block.yml b/grc/misc_utils/gsm_message_file_source.block.yml
new file mode 100644
index 0000000..047ea28
--- /dev/null
+++ b/grc/misc_utils/gsm_message_file_source.block.yml
@@ -0,0 +1,23 @@
+# auto-generated by grc.converter
+
+id: gsm_message_file_source
+label: Message File Source
+
+parameters:
+-   id: filename
+    label: Source file
+    dtype: file_open
+    default: /tmp/output.msg
+
+outputs:
+-   domain: message
+    id: out
+
+templates:
+    imports: import grgsm
+    make: grgsm.message_file_source(${filename})
+
+documentation: |-
+    This block outputs gsm messages stored in a file.
+
+file_format: 1