RFR: Add tester bot and ci module

[Erik Helin]

Hi all,

please review this slightly larger patch that adds the `tester` bot and the `ci` module. The `tester` is the bot supporting the `/test` command in a PR, for example writing `/test tier1`. I wanted to name the bot `test` but it was to annoying to get that work with the already present `test` module �� 

Thanks,
Erik

## Testing
- [x] `sh gradlew test` passes on Linux x64
- [x] Added a bunch of new unit tests for the `tester` bot (`ci` module is just an interface)
- [x] Manually tested to deploy the bot

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Commits:
 - 436deb55: Add tester bot and ci module

Changes: https://git.openjdk.java.net/skara/pull/248/files
 Webrev: https://webrevs.openjdk.java.net/skara/248/webrev.00
  Stats: 3356 lines in 39 files changed: 3356 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/skara/pull/248.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/248/head:pull/248

PR: https://git.openjdk.java.net/skara/pull/248