Update Custom Fields Initializer for Netbox 2.7 ...

The custom field database model has changed in Netbox 2.7.
Therefore the initializer code, that was used before, broke.
As a user, you will need to update your custom_fields.yml file as
follows:

- type must be lowercase
  - the `selection` type was changed to `select`
- the filter_logic must be lower case

This is to achieve compatibility with the naming schema that
Netbox uses internally. It allows us to become forward compatible
in case Netbox ever introduces a new type for custom fields.

See the diff of this commit for further information how this is meant.

Fix initializers

fix deprecated value

Merge branch 'master' into auto_weight_choices

Add support for auto_weight counter on choices when loading selection field from custom_fields.yml ...

This also fixes a bug when using the same value for 2 different custom fields breaks becuase it tries to
create a new CustomFieldChoice object instead of reusing the one that already exists.

Implement fix for field 'filterable' that was broken. Added new custom field parameter 'filter_logic'

✨ Include Initializers ...

Initializers are startup scripts for common tasks like creating custom
fields. These are problems many users of Netbox Docker potentially face
and are therefore worth sharing.