specfile: complete cleanup (according to FPG) & package layout update
    
      The specfile has been completely rewritten from the ground up, to
      comply with Fedora Packaging Guidelines, and to incorporate comments
      from upstream. The subpackage layout was also updated into more sane
      and more granular scheme.
    
      The changes are described more in detail below:
      (Justifications for them can be found in the specfile's comments.)
    
      * libijs -- the IJS library has been debundled and is now provided
        as a separate package: https://src.fedoraproject.org/rpms/libijs
    
      * libgs -- new separate package, created from Ghostscript's shared
        library. It contains all necessary files for other software/packages
        that are build upon Ghostscript's functionality.
    
      * libgs-devel -- new separate subpackage, for development purposes or
        Fedora's build process. The 'ghostscript-devel' is still provided
        for now as a virtual subpackage.
    
      * ghostscript -- is no longer a metapackage. It's a regular package
        instead, and it contains Ghostscript's binaries as well as some
        typical conversion scripts people are used to (and expect to have
        installed together with Ghostscript by default).
    
      * ghostscript-tools-fonts -- new subpackage that contains 3 scripts
        that are useful only for people who are working with AFM, PFB or PFA
        files (conversions usually).
    
      * ghostscript-tools-printing -- new subpackage that contains only
        utilities for formatting and printing text files using either
        Ghostscript, or BubbleJet, DeskJet, DeskJet 500, & LaserJet printers.
    
      * ghostscript-core -- has became an empty metapackage for upgrade
        purposes. It will be removed once Fedora 28 is EOL, and all other
        packages has updated their specfiles to require correct subpackages.
    
      * LPR setup scripts are no longer being shipped. In case people still
        need those, then 'ghostscript-tools-lpr' will be created for it.
    
      * examples/ from 'ghostscript-doc' are no longer shipped.
    
      * Support for /usr/share/ghostscript/conf.d/ folder was dropped to use
        Ghostscript's default choice for rendering of CJK glyphs, which is
        Google Droid Sans Fallback font. In case this proves insufficent,
        the conf.d/ folder support will be re-established.
    
      * Symbolic links for direct resources locations have been added to
        speedup Ghostscript's startup time
    
      * Ghostscript's search path was updated to include only fonts
        locations, which will be used only as a backup (in case of broken
        symbolic links).
    
      * Documentation and resources paths no longer contain version string
        inside of them.
    
      * Ghostscript itself (as a whole) has been completely debundled (to a
        point where it still makes sense). It newly requires these packages:
    
        https://src.fedoraproject.org/rpms/adobe-mappings-cmap
        https://src.fedoraproject.org/rpms/adobe-mappings-pdf
        https://src.fedoraproject.org/rpms/libijs
        https://src.fedoraproject.org/rpms/urw-base35-fonts
    
      * As a result of debundling, 'poppler-data' is no longer a requirement
        for Ghostscript, and it is no longer necessary to do a rebuild of
        'poppler-data' when Ghostscript is rebased.