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/gsm.tree.yml b/grc/gsm.tree.yml
new file mode 100644
index 0000000..4aee993
--- /dev/null
+++ b/grc/gsm.tree.yml
@@ -0,0 +1,58 @@
+'[GSM]':
+- Receiver:
+  - gsm_receiver
+  - gsm_receiver_with_uplink
+  - gsm_cx_channel_hopper
+  - gsm_fcch_burst_tagger
+  - gsm_sch_detector
+  - gsm_fcch_detector
+  - gsm_clock_offset_control
+  - gsm_input
+- Transmitter:
+  - gsm_txtime_bursts_tagger
+  - gsm_txtime_setter
+  - gsm_gmsk_mod
+  - gsm_preprocess_tx_burst
+  - gsm_gen_test_ab
+- Transceiver:
+  - gsm_trx_burst_if
+- Logical channels demapping:
+  - gsm_universal_ctrl_chans_demapper
+  - gsm_bcch_ccch_demapper
+  - gsm_bcch_ccch_sdcch4_demapper
+  - gsm_sdcch8_demapper
+  - gsm_tch_f_chans_demapper
+  - gsm_tch_h_chans_demapper
+- Decryption:
+  - gsm_decryption
+- Decoding:
+  - gsm_control_channels_decoder
+  - gsm_tch_f_decoder
+  - gsm_tch_h_decoder
+- Flow control:
+  - gsm_burst_timeslot_splitter
+  - gsm_burst_sdcch_subslot_splitter
+  - gsm_burst_timeslot_filter
+  - gsm_burst_sdcch_subslot_filter
+  - gsm_burst_fnr_filter
+  - gsm_burst_type_filter
+  - gsm_dummy_burst_filter
+  - gsm_uplink_downlink_splitter
+- Utilities:
+  - gsm_bursts_printer
+  - gsm_burst_file_sink
+  - gsm_burst_file_source
+  - gsm_collect_system_info
+  - gsm_message_file_sink
+  - gsm_message_file_source
+  - gsm_extract_system_info
+  - gsm_extract_immediate_assignment
+  - gsm_extract_cmc
+  - gsm_extract_assignment_cmd
+  - gsm_controlled_rotator_cc
+  - gsm_controlled_fractional_resampler_cc
+  - gsm_message_printer
+  - gsm_clock_offset_corrector_tagged
+  - gsm_msg_to_tag
+  - gsm_tmsi_dumper
+  - gsm_burst_to_fn_time