A piece of sugar for ost.table fans! Selection method which returns

a sub-table with every row, that fulfills a certain ost-style query.
It is still in development stage!
TODO: Right now every full logical statement has to be embraced by
brackets => 'col_a<100 and (col_b=50 or col_c>1000)' will throw an
error. One has to provide a query in the form:
'(col_a<100) and ((col_b=50) or (col_c>1000))'