Release scan2pdf-v2.6

Changes:
- Added option '-t/--prompt-timeout VALUE' (with VALUE in seconds); when
  specified, user prompts time out after the specified duration, allowing
  for automatic, time-based continuous scanning (useful for manual duplex
  and/or batch mode)
- Added option '-i/--initial-prompt' which issues a user prompt before the
  first scan operation (e.g. before odd pages for manual duplex, before first
  document in batch mode)
- Redistributed short options to free up letters for added features (mainly
  '-t' for '--prompt-TIMEOUT'; additionally, '-p' seemed more fitting for
  '--outfile-PATTERN')
- Renamed option '-a/--batch-scan' to '-a/--batch-mode' (seemed more fitting)
- Added defaults for all command line options to usage information (before,
  defaults for flags like manual duplex, batch mode, etc. were missing)
- Added all possible configuration items to configuration file (before,
  flags like manual duplex, batch mode, etc. were omitted)
- Applied several minor fixes (prints, comments, error messages)

Release scan2pdf-v2.5

Changes:
- Added option '-u/--manual-duplex' to facilitate scanning double-sided
  documents with devices that lack hardware support for duplex scanning
- Added Service Menu for KDE file managers Konqueror and Dolphin for
  convenient one-click scanning to PDF file via context menu entries
- Reduced 'printx()' functions to one-liners, output warnings and errors
  to stderr

Release scan2pdf-v2.4

Changes:
- Changed workflow to either use 'scanimage'+'convert' (preferred) -or-
  'scanimage'+'tiffcp'+'tiff2pdf' (fallback); 'convert' is preferred as
  'tiff2pdf' might get removed from LibTIFF in the future (see https://
  bugs.gentoo.org/914232)
- Updated dependency requirements in 'README.md' to reflect new workflow
  (now, either ImageMagick -or- LibTIFF is required)
- Added output options for 'convert' equivalent to those currently used for
  'tiff2pdf' (i.e. ZIP compression -or- JPEG compression, quality 95)
- Added command options to 'Scan settings/parameters' listing printed to
  console

Release scan2pdf-v2.3

Changes:
- Added option '-a/--batch-scan' to allow scanning multiple documents in one
  go, prompting user in between documents (depends on option
  '-o/--outfile-pattern' for output file naming)
- Added option '-o/--outfile-pattern' that allows specifying OUTFILE command
  line argument as printf-style pattern (e.g. '~/Documents/Scan_%05d.pdf')
  that is used to automatically determine the next available output file name
  by incrementing the integer part of the pattern
- Reordered configuration items to better highlight which settings to use for
  which paper size
- Removed configuration items that only make sense to be modified via command
  line options from configuration file ('BATCH_SCAN_DEFAULT',
  'OUTFILE_PATTERN_DEFAULT', 'KEEP_TEMP_DEFAULT')
- Eliminated need to 'cd' to temporary directory by adding path to temporary
  directory to '--batch=' template of call to 'scanimage'
- Added '--' to explicitely end option parsing to all external commands that
  support it
- Applied a few minor tweaks to printed output (wording, spacing)
- Extended headers in script and configuration file to 80 characters
- Reformatted 'README.md' and 'CHANGELOG.md' to be more readable when viewed
  in a simple text viewer/editor

Release scan2pdf-v2.1

Initial release (versions prior to v2.1 have not been published)