BUG: fixed append for dataframe with multi-column
Merge pull request #6167 from wabu/append-multi-fix

append to existing table with mulitindex fix
TST: sparc fixes in datetime weirdness
test for read_columns with start/stop
start/stop for read_column
fixed read_coordinates with filter in selection
select_coords with start stop
fix for select_as_multiple with start/stop
test for filter with select_as_coordinates