code style: operator spacing

Apply rector fixes to inc/Form

Fix undefined array keys when displaying revisions

show checkbox and radio before its label text

PSR-12 coding style

form prefill: honor empty values

when a form was submitted with an empty input, that data should still
overwrite the preset value.

Form: more flexible label handling #1312

You now can add labels that don't wrap around inputs, but you have to
ensure IDs are properly assigned yourself.

The Label class has been renamed to LabelEl

Form: more flexible label handling #1312

You now can add labels that don't wrap around inputs, but you have to
ensure IDs are properly assigned yourself.

The Label class has been renamed to LabelElement to reflect the naming
scheme of the other elements.

show more ...

Form: correctly set type attribute for inputs #1312

fixed label output

started with the compatibility layer

added a first few tests.

this is far from comprehensible, but should give an idea how the new
library works and how to write tests

start of rewriting the form handling

This is jsut a small beginning. Not all elements are there, yet. It's
also completely untested so far.