JIRA INFRA-545

This is to be used for stack of switches only

- a stack_member is linked to an host (device_type has to be "Switch")
- a stack_member is an integer between 0 and 9 (included) or can be None
- the couple (host_id, stack_member) must be unique

JIRA INFRA-267

The class "is-invalid" is removed on all type=text input
on keyup event.

JIRA INFRA-285