Fix: add unique ids in postgresql database plugin and response event structure

[drshrey]

Fixes:

• postgresql plugin to use a working format for returning artifacts
• including the database plugin inside main.go
• unique ids for postgres DB names and users to allow multiple db installations for one project

Future Improvements:

• better testing to cover full scope of practical failure cases (https://github.com/codeamp/circuit/issues/453)

[codecov[bot]]

Codecov Report

Merging #451 into master will decrease coverage by 0.05%. The diff coverage is 67.56%.

@@            Coverage Diff             @@
##           master     #451      +/-   ##
==========================================
- Coverage   58.07%   58.02%   -0.06%     
==========================================
  Files          56       56              
  Lines        5799     5820      +21     
==========================================
+ Hits         3368     3377       +9     
- Misses       2090     2096       +6     
- Partials      341      347       +6

[aballman]

remove spew