Support new grid

[Herst]

Adds the following

• W009 (empty spacer column)
• E005 (row and col on same element)
• E012 (input-group and col on the same element)
• E013 (invalid children of rows)
• E014 (invalid parent of cols)
• E029 (col 0 classes)
• E037 (float classes and col)
• E051 (float style and col)
• E052 (float style and row)

All of them existed already in the original Bootlint.

ToDo

• Code
• Tests
• Documentation (Wiki)

Notes

• Simplified the empty column message generation a lot. Since the user is pointed to the Wiki it cold be explained in more detail there.
• Removed some tests. Explanation will follow.

(#2 was on the old branch.)