forms/vm: Use timestamp for names of temporary templates.

Refs #12423.
models: Add "temporary" field on templates, and migrate.

Refs #12423.
views/vm_template: Don't show temporary templates.

Refs #12423.
forms/vm: Save temporary templates with the correct flag.

Refs #12423.
models: Establish VMTemplate.set_name(), and test.

Factors out setting of temporary field for testing.
Dont save temporary templates. They arent used yet.

refs #12423