Order ParamConverterProviders and ExceptionMappers by @Priority

Currently, when ResteasyProviderFactory registers a new ParamConverterProvider, it adds it to the end of a list, which means that a new ParamConverterProvider with a high priority, according to a @Priority annotation, could get tried after a lower priority ParamConverterProvider. The list should be ordered by decreasing priority.

Also, when ResteasyProviderFactory registers a new implementation of ExceptionMapper<Exception>, it overwrites any implementation that is already registered. That should happen only if the new implementation has a higher priority, according to a @Priority annotation.