whitespace pattern proof of concept

[jgrey4296]

This adds basic support for whitespace patterns by altering how regex's are compiled, no longer escaping + and * symbols. To handle this when rewriting lines, a replacement_pattern is added to Pattern, allowing a pre-formatted version string to be subbed into the matching line directly. This means no changes are made to _format_segment.

A couple of tests are added to show it working, and test_v1_error_bad_pattern breaks... but I have no idea why because I didn't touch v1 pattern code.