support multi initialize and multi claim

[jeroenmaelbrancke]

At this moment we need to initialize one disk at the time and claim all the disks afterwards.
Can you change this to initialize and claim a couple of disks?

For example:
Initialize 5 disks on node x.
Claim only 3 disks for this backend.
or
Initialize all disks except one disk and claim x amount of disks.

Maybe you can use also a pop-up with an overview of current disks per node and give use the option via checkboxes which disks we want to initialize or claim.

If you want to make it more advanced create a pop-up with an overview of all the nodes and their disks. Initialize/claim x disks spread across x nodes.

[wimpers]

Note to self:

• Initialize all can't work if you have a dm-0 partitions (see dm-0 crypt device not recognized framework#1647)
• option to select 2/6 disks for a backend

[JeffreyDevloo]

I think the request is more for a multi-select on the backend page
Similar to how you multi-select things on Phone applications. You press a button, multi-select is invoked and all items you click are queued for initialization/claiming