Resolve feature backlog

• Make sure that the generated parser is the same as the bootstrap
  parser.
• Honor grouping in pattern expressions with the semantics of
  re.findall(pattern, text)[0]. Now groups that should not be
  returned when parsing should use the (?:) syntax. Now patterns
  align with Python re independently of the
  @@ignorecase setting for the grammar.
• Allow {} interpolation in `constant[ expressions with the
  semantics of ]{.title-ref}[str.format()]{.title-ref}`
• Add [constant]{.title-ref} as a multiline version of
  `constant`.
• Add ^[constant]{.title-ref} and ^`constant[ as syntax
  for an `alert]{.title-ref} expression. Alerts produce no tokens bug
  get registed in [parseinfo]{.title-ref} records.
• BUG: make the -> skip expression always stop at EOF.
• Make the -> skip expression go over comments, and not log while
  skipping.
• Patch problem with pickling FailedCut while running parsing in
  parallel.
• Optimize model pickling and parallel processing to reduce runtime
  and memory use with parproc
• Add a representation of ~ cut expressions to parse traces