A simple integration to OpenStack Swift.

Added a new backend 'swiftstore'. This backend store files
to OpenStack Swift object storage.

### Pre-requirement
Install the python-swiftclient
```
pip install swiftclient
```

### Configuration
modify ini file to use swift backend.
```
# OpenStack Swift storage:
ofs.impl = swift
ofs.auth_url = http://localhost:5000/v2.0
ofs.user = admin
ofs.passwd = admin
ofs.tenant = admin
```