Added "anyContentVersion" and anyContentVersion  matchers to e2e framework
Added "anyContentVersion" and anyContentVersion  matchers to e2e framework

refs https://github.com/TryGhost/Toolbox/issues/335

- Similarly to `anyEtag` pattern for `etag` headers there's a need to match dynamic content-length and content-version headers.
- The `anyContentLength` is the same as `anyStringNumber` matcher, created a separate one to show the intention over a function when reading the code (maybe we could introduce something like floating number range matcher in the future to be more precise in situations where we expect the content-length to float in +-2 length range)

TryGhost/Ghost,TryGhost/Ghost,TryGhost/Ghost