Revise the interface of loading defaults to make it more compact!

[ZPYin]

@HolgerPollyNet

The reasons for making the changes are twofold:

1. Defaults and polly configs can be backup together. This is very convenient to setup a new development environment.
2. Configuring the pollynet_processing_chain_link.txt becomes easier, as only the polly defaults file name needs to be provided, compared with setting a new matlab function for loading the defaults.

[ZPYin]

New folder structure of config is as below:

config
├── pollyConfigs
│   └──  polly_global_config.json
├── pollyDefaults
│   ├── template_polly_defaults.json
│   ├── template_polly_overlap_355.txt
│   └── template_polly_overlap_532.txt
├── template_pollynet_processing_chain_config.json
└── template_pollynet_processing_chain_link.txt

Meanwhile, only the polly defaults filename needs to be provided in configuring the pollynet_processing_chain_config_link.txt.

Before

pollyxt_tau,2019-09-10 00:00:00,2019-11-03 23:59:59,pollyxt_tau_config_20190910.json,pollynet_processing_chain_pollyxt_tau.m,Move to Tel Aviv Israel,pollyxt_tau_read_defaults.m

After

pollyxt_tau,2019-09-10 00:00:00,2019-11-03 23:59:59,pollyxt_tau_config_20190910.json,pollynet_processing_chain_pollyxt_tau.m,Move to Tel Aviv Israel,pollyxt_tau_defaults.json