hack files on VM delete

[OndrejHome]

Idea:

• Support hack files also on VM deletion as the hack files on creation might create something that users would like to clean up once the machine is deleted.

Implementation:

• delete hack_file will be optional and only available if create hack_file exists

Updated commands:

• fast-vm import_image ,image_path> [ ]
• fast-vm delete []

Location of delete hack_file will be same as regular hack_file with prefix 'delete-'.

[OndrejHome]

testing version in 0d68d17edff35c22810a4dca36f635361468386f