Release based on Gerrit plugin API 2.13.1

Release 2.13.1

Bug fixes:

#64

Note When upgrading to 2.13 release line, release 2.13.2 or later must be used, because earlier 2.13.x releases have regressions in OAuth extension point that prevent this plugin (or any other OAuth provider-plugins) from working. Particularly, these regressions were fixed:

• #63
• #69
• #71