Return original format from convert and layout function

[AliaksandrDziarkach]

According to epam/ketcher#3393 backend should return original format by using "original_format": "$format" (where $format is one of the currently support content types)

Add two new options in "options":

1. input-format - set input format to load from. same values as used in output-format
2. output-content-type - if set to 'application/json' - functions will return json with next format:
   {
   "struct": output_molecule,
   "format": output_format,
   "original_format": original_format,
   }
   Where 'output_molecule' - molecule in output format, 'output_format' - output format name like 'chemical/x-daylight-smiles', 'original_format' - format used to load molecule.