model/error_code library

1. call_log_fetcher package
2. documentation
3. model/error_code.dart

call_log_fetcher package

1. Libraries
2. call_log_fetcher
3. call_log_fetcher_method_channel
4. call_log_fetcher_platform_interface
5. model/call_log_entry
6. model/call_log_query
7. model/error_code
8. permission_handler