[Jenkins-infra] Accountapp improvements

[Olblak]

Hi,

I propose some modifications to the accountapp to better support the
next board election.

Those modifications include
  * A view to get election result
  * Use Single Transferable Vote algorithm to count votes result.
  * Only allow one-year-old users account to vote

I explain more in detail in this PR
"https://github.com/jenkins-infra/account-app" and how to test locally
(mainly require docker).

I would be interested by any feedback (modifications, improvements,...). 

Just be indulgent with my java/css skills :D

Some links for the context:
  * https://github.com/jenkins-infra/account-app/pull/108
  * https://issues.jenkins-ci.org/browse/INFRA-536
  * https://wiki.jenkins.io/display/JENKINS/Board+Election+Process


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