Release 0.3.1

Bug #51 concerning type-hints is fixed in this release.

Minor API changes:

• The header parameter classes are now dataclasses
• type_ is now type on initializing Definitions (Attribute as type already)
• format_string is now format Attribute on Definitions (it is not used so far anyway)
• When creating a SDDS-instance, a ValueError is raised, if more than one parameter with the same name is defined.

What's Changed

• CI Updates by @fsoubelet in #50
• raise and test error by @JoschD in #54
• Fix typehints by @JoschD in #55

Full Changelog: 0.3.0...0.3.1