Added cpp code generation capability to Rx blocks

[AlonSpinner]

Can also be merged to master (no conflicts)
from the updated README: (do not merge the README.md)

We implement c++ code generation capability to all Rx blocks in this repo.
This means adding the following lines to each of the blocks' .yml files:

• flags: [python, cpp]
  

• cpp_templates: 
  includes: ['#include <gnuradio/lora_sdr/<BLOCK_NAME>.h>'] 
  declarations: 'lora_sdr::<BLOCK_NAME>::sptr ${id};' 
  make: 'this->${id} = lora_sdr::<BLOCK_NAME>::make(<PARAMS>);'
  packages: ['gnuradio-lora_sdr']
  link: ['gnuradio::gnuradio-lora_sdr']
  translations:
     'False': 'false'
     'True': 'true'
     \[: '{'
     \]: '}'
  

notice the <BLOCK_NAME> and tag.
for example you can look at /grc/lora_sdr_frame_sync.block.yml where it is already implemented

Rx Blocks:

• lora_sdr_fft_demod.block.yml
• lora_sdr_gray_mapping.block.yml
• lora_sdr_deinterleaver.block.yml
• lora_sdr_hamming_dec.block.yml
• lora_sdr_header_decoder.block.yml
• lora_sdr_dewhitening.block.yml
• lora_sdr_crc_verif.block.yml

[tapparelj]

Hi,
Thank you for adding the support of cpp output in grc. All works fine for me!
For now, I'll merge it with the sf5/6 branch and then integrate this branch into the main one later, once the sf5/6 transmission are properly received by commercial chips.

[tapparelj]

Thanks for the Tx blocks!
There were a few mistakes in the order of parameters, but nothing that couldn't be fixed.
I've also added a tx_rx test flowgraph for the C++ output