Several enhancements

[almarklein]

• Implements FormLayout using css grid. Closes Implement form layout using CSS instead of TABLE #422.
• Implements new GridLayout using css grid.
• Implements new MultiLineEdit.
• Support code for freezing.
• Docs. Closes outernode and node documentation for developers #552
• TODO: see if freezing can be implemented as simple as App.freeze(). -> DONE in Make freezing easier #559

[damienflament]

I think implementing that layout using a <table> is not semantically correct. I would rather have used the CSS display property with its values table-row, table-column, table-cell, etc.

[almarklein]

I think implementing that layout using a <table> is not semantically correct.

Which one? The FormLayout was implemented with <table> before this PR, but afterwards, no layout uses table anymore.

[damienflament]

Arf. My bad. I misread the code within your PR and mixed up the old BaseTableLayout implementation and the new GridLayout.

[almarklein]

Hehe, no problem. Thanks for speaking up nonetheless :)

[almarklein]

merging now, will look at easier freezing in a separate PR.

[almarklein]

Also see #559