1.0.0 release

[JeroenDeDauw]

Making use of the first breaking release since 2013 to correct the version number. This has already been done for most other components.

There is some disagreement by @thiemowmde, though I personally do not understand what the exact objection is.

As per semver.org:

How do I know when to release 1.0.0?

If your software is being used in production, it should probably already be 1.0.0. If you have a stable API on which users have come to depend, you should be 1.0.0. If you're worrying a lot about backwards compatibility, you should probably already be 1.0.0.

[thiemowmde]

-2. I switched back to 0.3 in #22 for a reason. I explained all arguments.

(12:28:33) Thiemo_WMDE: see DataValues/Interfaces#14
(12:29:15) Thiemo_WMDE: all the datavalue components are far from becoming "official".
(12:30:00) Thiemo_WMDE: they ARE still in a pre state. switching to a "final" version number gives the wrong impression.
(12:49:18) Thiemo_WMDE: the datavalue components are all still in flux and will change in the near future. we will rework them and have other, easier to understand splits between the components. we are talking about this since months. 0.3 is not wrong. it's more honest. it reflects the fact that the component will drastically change before an "official" 1.0 release.

There is no good reason to switch to a much more "official" looking version number. 0.3 is not wrong. It was like that for years. There is no urgent need to change it right now. Let's please, please, please keep this as simple as possible. Nothing is blocking us from switching the version number scheme with a later release.

[addshore]

I tagged 0.3.0 to unblock some stuff.
We can still tag 1.0.0 whenever we want / now / the next release

[thiemowmde]

Resubmitted as #67.