RFR: cli: add --atomic and --manual to git-pr-integrate

[Erik Helin]

Hi all,

please review this patch that adds the switches `--atomic` and `--manual` to `git-pr-integrate`. These flags will simply just append either "atomic" or "manual" to the `/integrate` pull request command that `git-pr-integrate` creates.

Testing:
- [x] Manual testing on Linux x64

Thanks,
Erik

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Commit messages:
 - cli: add --atomic and --manual to git-pr-integrate

Changes: https://git.openjdk.java.net/skara/pull/1075/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=1075&range=00
  Stats: 29 lines in 1 file changed: 28 ins; 1 del; 0 mod
  Patch: https://git.openjdk.java.net/skara/pull/1075.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/1075/head:pull/1075

PR: https://git.openjdk.java.net/skara/pull/1075