multi DBF fix

Existing code assumes a flat archive structure for shapefiles, which was breaking things. Another vote for moving unzipping/file manipulation code outside of the `conform` tool.

```
Archive:  be-flanders.zip
  Length     Date   Time    Name
 --------    ----   ----    ----
    10726  12-06-14 00:47   Gebruik_CRAB_Adressenlijst.pdf
   351888  12-06-14 00:47   Leesmij_CRABADRLST.pdf
    55764  12-06-14 00:47   Meldingsformulier.rtf
    16160  12-06-14 00:47   Meta_CRAB_Adressenlijst.pdf
    49914  12-06-14 00:47   Meta_CRAB_Adressenlijst.xml
931079104  12-06-14 00:47   Shapefile/CrabAdr.dbf
    17408  12-06-14 00:12   Shapefile/CrabAdr.lyr
      489  12-06-14 00:12   Shapefile/CrabAdr.prj
 94116360  12-06-14 00:47   Shapefile/CrabAdr.shp
 26890460  12-06-14 00:47   Shapefile/CrabAdr.shx
     2680  12-06-14 00:12   Shapefile/CrabAdr.WOR
     5768  12-06-14 00:47   Shapefile/extra/CrabAdrLktHERKOMST.dbf
 --------                   -------
1052596721                   12 files
```