format: handle line-count properly for format2

format: handle line-count properly for format2

There is along standing bug that the linecount appears to be elevated in
a formatted view anywhere but at the start of the line.
Also word counts don't work properly.

Now that we can attach line counting to a view, this can be fixed.

Also: allow view-based linecount to be disabled by parent.  It is
notably slower and for notmuch search view it is too slow.

Signed-off-by: NeilBrown <neil@brown.name>