Read multiaperture daophot file

I have added a few lines of code in get_cols() function of daophot.py to enable it to read daophot files which contain multiple aperture data.

daophot3.dat is a sample daophot file with multiple aperture data.
Also added a test_daophot_multiple_aperture() in tests/test_read.py  for test.

This is related to Issue #904
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