removed unused and some very opinionated code from the forms theme

[kevinpapst]

Description

This is a BC break if you used the form these provided by this bundle.
Otherwise it is just a cleanup of code that does not belong here.

Types of changes

• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• I updated the documentation (see here)
• I agree that this code will be published under the MIT license

[kevinpapst]

The code which I removed should not be in here, it is the responsibility of the project to decide how your forms should look like. Floating labels work different from regular forms. Then also there were leftovers from certain datepicker-picker libraries in there, which should not interfere with your customizations.

@wucherpfennig @cavasinf can you have a quick look if your projects are negatively affected / if the docs are sufficient to clarify the process.

[wucherpfennig]

Sorry for not providing feedback. I did check and it seams reasonable. I will find out as soon as there is an obvious error aka "scream testing" 😉