Allow setting needFileUpdate in json body for /api/deployments

This is related to #1175

I found that setting `needFileUpdate = false` and passing it through to the DeployAsync method in the DeploymentManager will avoid the need to checkout the master branch or a specific revision and do an incremental deploy just like with `git push`.
In my scenario the repository has been updated with additional commits and the repository is checked out on the master branch (latest commit - which I want to deploy), so I don't need to do any additional checkouts. Ideally I would be able to do incremental updates, which this setting seems to allow.

Let me know what you think of this PR.

Thanks!