Singledish_config keys ignored by the key reader function

[astrojysun]

The current singledish pipeline expects "singledish_config" keys in the config_definition file. However, the read_config_key function in utilsKeyReaders.py does not read them because "singledish_config" is not among the expected keyword list. This also manifests as the following error messages when running the pipeline

[ERRO] [          read_config_key] Got an unexpected parameter key. Line is:
[ERRO] [          read_config_key] singledish_config   tp  {'bl_order':1,'chan_dv_kms':2.5}

Happy to help address this -- it should just be a few lines (hopefully).