RFR: bots: add census bot

[Erik Helin]

HI all,

please review this patch that adds a census syncing bot.

Thanks,
Erik

-------------

Commit messages:
 - bots: add census bot

Changes: https://git.openjdk.java.net/skara/pull/796/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=796&range=00
  Stats: 287 lines in 7 files changed: 287 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/skara/pull/796.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/796/head:pull/796

PR: https://git.openjdk.java.net/skara/pull/796