RFR: 1118: The Skara PR bot should not block on a CSR if not enabled for a repo [v3]

[Guoxiong Li]

> Hi all,
> 
> This patch adds a config item `enable-csr` for the PullRequestbot and then the `CSRCommand` firstly checks whether the csr is enabled. If not enabled, the `CSRCommand` will reply a message about it.
> 
> Thanks for taking the time to review.
> 
> Best Regards,
> -- Guoxion

Guoxiong Li has updated the pull request incrementally with one additional commit since the last revision:

  Fix tests

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

Changes:
  - all: https://git.openjdk.java.net/skara/pull/1308/files
  - new: https://git.openjdk.java.net/skara/pull/1308/files/3e6d8064..d871f1bd

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=skara&pr=1308&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=skara&pr=1308&range=01-02

  Stats: 12 lines in 2 files changed: 0 ins; 0 del; 12 mod
  Patch: https://git.openjdk.java.net/skara/pull/1308.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/1308/head:pull/1308

PR: https://git.openjdk.java.net/skara/pull/1308