Big assertion capture refactoring.

- moved as much logic out of the macros as possible
- moved most logic into new ResultBuilder class, which wraps ExpressionResultBuilder (may take it over next), subsumes ResultAction and also takes place of ExpressionDecomposer.

This introduces many SRP violations - but all in the name of minimising macro logic!

include/internal/catch_common.hpp

@@ -77,7 +77,7 @@ namespace Catch {
     void throwLogicError( std::string const& message, SourceLineInfo const& locationInfo ) {
         std::ostringstream oss;
         oss << locationInfo << ": Internal Catch error: '" << message << "'";
-        if( isTrue( true ))
+        if( alwaysTrue() )
             throw std::logic_error( oss.str() );
     }
 }