Possible fix for bug 913 -GRASS Backend multiple
UTF-8 default encoding fix

Without this fix, it was not possible to request non-base64-encoded
binary files (images as well as zipped shapefiles) as output of GRASS
processes.
Refactored stream reader
Added image/geotiff mimetype to genericfileparser
Removed unused functionality
Some refactoring of the GRASS 7 backend.

Fixed a bug in GenericFileData with unzipping files.