Add NS/AS KEK labels, AS-ID, NetID to device create form

[bafonins]

Summary

References #1134

Changes

• Add application_kek_label, network_kek_label, application_server_id and net_id fields to the device create form
• Update validation schema accordingly

Notes for Reviewers

Since #579 is taking longer than expected and still requires some work, I think we should make the create and edit forms consistent. After #1616 the user can edit those fields, while it is still not possible to edit them while creating an end device.

Checklist

• Scope: The referenced issue is addressed, there are no unrelated changes.
• Compatibility: The changes are backwards compatible with existing API, database and configuration, according to the stability commitments in README.md.
• Testing: The changes are covered with unit tests. The changes are tested manually as well.
• Documentation: Relevant documentation is added or updated.
• Changelog: Significant features, behavior changes, deprecations and fixes are added to CHANGELOG.md.
• Commits: Commit messages follow guidelines in CONTRIBUTING.md, there are no fixup commits left.

[coveralls]

Coverage increased (+0.005%) to 73.316% when pulling 2cfac35 on feature/device-form-fields into 4001d2f on master.

[kschiffer]

LGTM