1. Enable config cache to improve config service performance, just set
config-service.cache.enabled to true in ServerConfig
2. Normalize the namespace name in case the one provided has character
case issue

1. add log output to console for config and admin service
2. remove dev, lpt, tooling logic
3. add default 2 seconds of initial delay to long polling

Date, Enum, Duration.

1. Add a release key generator to generate human-readable release keys
2. Add retry policy for client long polling
3. Move eureka url config to database

1. Refactor apollo client code according to  @qmwu2000's comments
2. Add config service integration tests
3. Add some cat events for config service
4. Fix several bugs