libsmartcols: multi-line cells refactoring

libsmartcols: multi-line cells refactoring

* move data wrapping code to column.c
* do data wrapping on one place when copy cell data to buffer
* use table cursor in affected functions
* calculate tree ASCII-art to wrapped data
* mark wrap_chunksize() callback as deprecated; library calculates
  the size itself from real data

Signed-off-by: Karel Zak <kzak@redhat.com>