Updating unikernels (modify arguments)

[PizieDust]

Provide UI and functionality to enable updating information about unikernels such as:

• changing/updating arguments
• updating block devices

[hannesm]

Related to #36

[hannesm]

I wonder whether a first version of this could be:

• add a new albatross command "restart_with_modified_arguments"
• add a "edit" button in the unikernel_single page where we can adjust the cpu, memory allocation, network assignments, and command-line arguments (basically transform that page into a form where fields are editable)
• then an "apply" button which sends the arguments to albatross -- but the unikernel image is left as-is

This wouldn't require any storage / unikernel image (i.e. what we need for #36). This could be a very similar form that we'd like for a "create unikernel" anyways.

A common operation/workflow is to upscale/downscale the memory requirement for a unikernel (as recently mentioned by @reynir).