detect_well_known_errors - Sort known errors/issues by rdep count.
detect_well_known_errors - Display the reverse dependency count.
Bump the required python version to 2.7.

... to support argparse in detect_well_known_errors.
optparse is deprecated in the current version.
detect_well_known_errors - Restore recheck and recheck-failed options.
detect_well_known_errors - Add PTS link to issue/error entries.
known_problems - Add INCLUDE parameters for re-based searching.
detect_well_known_errors - Use python re for fast kpr generation.

Run with full .kpr replacement is 2 1/2 minutes vs. 28 minutes for
grep, per section, with stale file buffers, and idle slaves.
Subsequent runs are 15 seconds vs. 60 seconds. Replacing the
packagesdb rdep sort with an alpha sort reduces that to 5 seconds.
detect_well_known_errors - Generate 'grep' help command from INCLUDE.

... and EXCLUDE, eliminating the need for COMMAND in known problem
definition files.
Remove COMMAND parameter from known_problems.
detect_well_known_errors - Changelog entry for re speedup.