Partial refactor to support substitutions in replacement strings as per spec

[throwanexception]

This is a partial refactor to bring uap-python closer to the specification in uap-core.

It supports regular expression backreferences for replacements for all parsers - uap-core has started to use these for UAParser and OSParser instances, and only DeviceParser currently supports. (note: this was true of the regexes I imported at the time - it appears uap-core had done some cleanup and this is somewhat better now)

I believe the spec (https://github.com/ua-parser/uap-core/blob/master/docs/specification.md)
does indicate that all matches from $1 to $9 should be honored for every
replacement.

Each parser contains a list of regular-expressions which are named regex. For each regex replacements specific to the parser can be named to attribute or change information. A replacement may require a match from the regular-expression which is extracted by an expression enclosed in normal brackets "()". Each match can be addressed with $1 to $9 and used in a parser specific replacement.

It additionally allows for a v3 replacement for UserAgent.

Refactored the class hierarchy so that it's sort of DRY, and moved MultiReplace to a module level function because it doesn't use self.

Looking forward to any feedback!

[ondras]

I think I solved the very same issue (in my own branch) using a simpler way: 6539b05

[throwanexception]

Thanks! I rebased and got your commit that fixes the issue, much better.

[masklinn]

Heya @throwanexception, it looks like the extraction and reuse of MultiReplace was independently performed in 7d61e38.

Assuming you still care, should I close this? v3 was never added to UserAgentParser, but there I would suggest getting a test case in uap-core for all implementations to leverage. Though I'm not sure uap-core currently has a "synthetic" test suite (which tests artificial cases against the spec rather than real-world parses), so that would probably require finding a real-world user agent which provides a use-case, as uap-python doesn't currently have one such test suite either (might be a good idea to add one as part of #102, unless -core is interested in adding one).