Add ability to query secrets using filter criteria

[llowrey]

Added listSecrets(Criteria criteria) to DockerClient and DefaultDockerClient. Essentially copied the code used by listConfig and Config.Criteria. I looked for unit test code for Secret and Config but didn't find any so I didn't include any tests. I have verified this functionality with my local swarm.

I also added CONFIG('config') to Event.Type so listening to the event stream doesn't fail when a 'config' event is received.

[codecov[bot]]

Codecov Report

Merging #1104 into master will decrease coverage by 1.89%. The diff coverage is 25.8%.

@@             Coverage Diff             @@
##             master    #1104     +/-   ##
===========================================
- Coverage     70.17%   68.27%   -1.9%     
- Complexity      791      805     +14     
===========================================
  Files           178      181      +3     
  Lines          3772     3947    +175     
  Branches        393      416     +23     
===========================================
+ Hits           2647     2695     +48     
- Misses          960     1077    +117     
- Partials        165      175     +10

[llowrey]

When I try to run tests locally, "testBuildInterruption" never completes. Any idea why?