Decide on a design for a single analyzer

[fastred]

When I started this project I really wanted to implement matching of connections between nibs and code. That's why the Analyzer protocol accepts the configuration containing metadata of all nib and swift files in the project. This won't scale to other warnings easily, though.

One of the ways forward that I can see is to use different configurations for different analyzers, e.g.:

• rename AnalyzerConfiguration to WholeTargetConfiguration
• add FileConfiguration containing only a URL of a nib file (this would be sufficient for https://github.com/fastred/IBAnalyzer/issues/1 and https://github.com/fastred/IBAnalyzer/issues/2)
• consider adding new configurations for new analyzers if needed