Replace Search class with Searcher and some other classes.

Decouple Searcher (Search) from results generation, matchers, preprocessors, file parsing etc. Create Searchee, SearcheeProvider,  SearchResult, ResultTextGenerator. Create MainWindowHelper with default configuration
Add Searcher tests
Cooperate with PersistanceManager

May contain traces of bugs
Merge branch 'Core'

Conflicts:
	FileScanner.PatternMatching/MatcherFactory.cs