New namespace manager

[xhebox]

• The current namespace manager used a double buffer mechanism. It records modifications in memory. With ETCD, this can be largely simplified by recoding modifications in ETCD instead.
  • manager: new namespace manager based on etcd #13 introduction
• Almost all frontend functionalities can be removed for now. Because of the lack of a working routing mechanism, all frontend/backend settings do not make sense. Also, it is not the current goal of session manager to parse SQL and blacklist/whitelist usernames/DBs.
  • config: remove useless fields, fix tests #12 remove useless fields
  • manager: new namespace manager based on etcd #13 further removing of useless code
• Security options per namespace will be introduced for later refactor of SNI routing.
  • manager: new namespace manager based on etcd #13 introduction
  • proxy: bring back auto tls cert creation #44
• Default namespace config and validation
  • manager: add basic UT for config manager #21 preparation
  • Create a default namespace if the namespace configuration is not specified #47
• misc
  • server: use json for API and internal storage #66

[xhebox]

Closed. It is mostly done. Refactors will not happen in the namespace manager.