[O] :minlevel for columnview dynamic block

[Joon Ro]

Hi,
I use columnview a lot with :id option to generate a table from sub-headlines 
of the tree that has an :ID: property. The issue is that even with 
:skip-empty-rows t option, the generated table always have one empty line on 
the top, for the headline for the tree itself.
It would be great to have something like a :minlevel option so I can exclude 
the tree headline.
Best,Joon