Results archiving

Added results archiving.
Result files are archived if the number of .json files exceeds n (specified in config). For each n files, a new archive is created (encoding specified in config).
Archive files are deleted after being sent to the server.
This is more intuitive - 
```
for file_count, result_file in enumerate(result_files):
    if file_count > self.config['results']['files_per_archive']:
```