Implement fallback strategies for corrupted PDFs

Some PDFs set, for example Recife, Fortaleza and Limeira are corrupted
and badly rendered. We still try to parse them but we need some quirks
implemented in the first place:

- Parse the X coordinate from the lower left corner of the map.
- Map margin detection when it is not standard.
- Interpolate the Y coordinate when it is corrupted based on pixel
  density.
Parse weird PDFs

Some PDFs in SP have each scanline of the map image in a different
object. This hack combines them in a attempt to read the map.
Set OCR confidence threshold
Set new values for minzoom and use bilinear filter when scaling

Unleash the Kraken.