Firmware and other file handling in PAPPL

Currently, PAPPL supports only raster printers and that too for very few specific input formats like JPEG and PNG. Adding the code in PAPPL for adding support for other file formats like PDF, GIF and SVG for uploading, and managing and removing already uploaded files. Adding the generalized code in PAPPL for uploading and managing custom PPD files as that in PostScript Printer Application, for all types of files that PAPPL supports including firmware files, for eg. by making use of callback function support to check the format of the file.