Several improvements to lb-format

based on user feedback, I made several improvements to lb-format (apart from minor improvements/fixes)

• try to ensure that a .clang-format file is present
  • if not found try to create it in the topdir of the git project, if any
• added mode to format all formattable files (both for --format-patch or in-place reformatting)
• added a --dry-run option to just show which files would be modified
• modified --format-patch to produce the patch file without modifying any file
• support stdout as --format-patch destination
• added --pipe mode to format from stdin to stdout

CC: @jonrob