Add a new driver, tests and documentation for CloudSigma API v2.0.

Also update existing driver for API v1.0 and other affected code:

- Update existing driver for API version 1.0 and prefix 1.0 classes with "1_0"
- Update existing 1.0 driver to support "region" argument. This way porting
  existing code to API v2.0 will be easier.
- Add new CloudSigmaNodeDriver class which can be instantiated directly. Which
  API version is used is dictated by the "api_version" kwarg which defaults to
  2.0.
- Add new libcloud.common.cloudsigma module which holds common functionality
  for CloudSigma drivers
- Update INSTANCE_TYPES to be a list so output of list_sizes() method is always
  returned in the same order.
Update CHANGES.
* add to node['extra']['block_device_mapping'] volume_id\n* fix in volume['extra'] parameter device (was incorrect xpath)\n* fix tests for coverage this

Signed-off-by: Tomaz Muraus <tomaz@apache.org>
Update CHANGES.