RFR: git-pr: add csr sub-command [v2]

[Erik Helin]

> Hi all,
> 
> please review this patch that adds the `git pr csr` sub-command that corresponds to the
> [`/csr`](https://wiki.openjdk.java.net/display/SKARA/Pull+Request+Commands#PullRequestCommands-/csr) pull request
> command. A contributor who prefers the command-line can now state that a pull request requires a
> [CSR](https://wiki.openjdk.java.net/display/csr) by running `git pr csr --needed`.  Testing:
> - [x] Manual testing on Linux x64
> 
> Thanks,
> Erik

Erik Helin has updated the pull request with a new target base due to a merge or a rebase. The pull request now
contains three commits:

 - Merge master
 - Add csr to GitPr.java
 - git-pr: add csr sub-command

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

Changes: https://git.openjdk.java.net/skara/pull/702/files
 Webrev: https://webrevs.openjdk.java.net/skara/702/webrev.01
  Stats: 103 lines in 4 files changed: 99 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/skara/pull/702.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/702/head:pull/702

PR: https://git.openjdk.java.net/skara/pull/702