Extend storage D-Bus API

[joseivanlopez]

Problem

The current result of the storage proposal is presented as a list of actions, which could make a bit complex to understand the overall picture of the resulting devices.

That list of actions is going to be replaced by a more visual representation of the devices. To make this possible, more information about the devices has to be exported on D-Bus.

• Part of https://trello.com/c/7TTVVquM.

Solution

Add the following information to D-Bus:

• The list of actions includes the SID of the affected device.
• The partition table exports the unused slots.
• The LVM devices (volume groups, physical volumes and logical volumes) are exported.
• The block devices includes their start block and also indicates whether the device is encrypted.
• The staging devices are exported.

NOTE: This PR goes to a feature branch instead of master.

Testing

• Added unit tests
• Tested manually

[ancorgs]

Isn't this explanation a bit too technical and a bit too close to the Y2Storage world? In fact, I would say that using the sid simply makes sense here and does not need that explanation about memory.

Just something saying this is the internal storage identifier and clarifying it's unique per device should be enough.

[joseivanlopez]

Yes, it is. But I would prefer to keep it as a warning. I see myself trying to use storage_device again for something, which is quite unsafe.

[ancorgs]

LGTM. I expected this to be more complicated, nice to see we actually have a nice infrastructure in place.