Remove #backtrace_clean_patterns.

This was deprecated a while ago. We've got deprecation specs in 2.99.
This patch removes it. This also renames the cukes.

Signed-off-by: Sam Phippen <samphippen@googlemail.com>
Make the .feature for backtrace_exclusion_patterns read better.

Signed-off-by: Sam Phippen <samphippen@googlemail.com>
Merge pull request #923 from samphippen/remove-backtrace-clean-patterns

Remove #backtrace_clean_patterns.