Write raw graph data into OpenStack.dot

For further processing it is useful to have to raw graph data.
Set 'style=filled' as default for all nodes

This will increase the readability of the generated dot file.
Horizon can use Trove, Sahara, and Heat
Barbican requires keystone
Merge pull request #7 from berendt/horzion_can_use

Horizon can use Trove, Sahara, and Heat
Merge pull request #8 from berendt/barbican_requires_keystone

Barbican requires keystone
Merge pull request #6 from berendt/global_node_defaults

Set 'style=filled' as default for all nodes
Merge pull request #5 from berendt/save_raw_data

Write raw graph data into OpenStack.dot
Ignore dot files