Added some missing exif tags

Added the following exif tags:
* 0x00fe -> NewSubfileType
* 0x00ff -> SubfileType 
* 0x0107 -> Threshholding
* 0x0108 -> CellWidth
* 0x0109 -> CellLenght
* 0x010a -> FillOrder
* 0x010d -> DocumentName
* 0x011d -> PageName
* 0x0118 -> MinSampleValue
* 0x0119 -> MaxSampleValue 
* 0x0120 -> FreeOffsets
* 0x0121 -> FreeByteCounts
* 0x0122 -> GrayResponseUnit
* 0x0123 -> GrayResponseCurve 
* 0x013c -> HostComputer 
* 0x0140 -> ColorMap
* 0x0152 -> ExtraSamples

Also removed from the dict a couple of duplicated tags.