New layout function sd:attr() - like @foo

This is to dynamically access attributes. With sd:attr('foo',$i) you
can access the attribute with the name @foo3, if $i is 3 for example.
B: multi line table head height calculation

When calculating the height of the head for table split, only the
first line was taken into account. Now we vpack the table, so we
get the height of the whole head.
F: Allow bookmarks on top level

Bookmarks were only allowed as a child of Textblock/Text. Now they
are allowed as a regular command. These bookmarks point to the current
page, whatever that means.