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_exception_translator_registry.hpp

@@ -41,6 +41,9 @@ namespace Catch {
                 throw;
 #endif
             }
+            catch( TestFailureException& ) {
+                throw;
+            }
             catch( std::exception& ex ) {
                 return ex.what();
             }