Remove - from select options

[Janpot]

deprecate argType.defaultValue and move it into the type definition as default, advantages:

• we can now use it in the property control.
• It's closer to its jsonschema counterpart
• it makes more sense logically, especially when we will expand into typing nested objects, we will be able to reuse it for nested properties
• deprecated as to not break existing custom components

This allows us to detect whether an enum type has a default value and therefore there shouldn't be a "empty" option in a select.

Fixes #1611

I'm leaving the id field selector of the datagrid as it is as it's a bit ore complex. The items are not predefined and an empty datagrid doesn't have any options to choose from anyway. Will look into this separately