Issue Summary

Scheduled trigger configured for deployment environment doesn't respect deployment from custom branch.

In Java Specs it's possible 

new ScheduledDeploymentTrigger()
                            .artifactBranch("branch")

but for YAML Specs trigger form has only expression

  triggers:
  - cron:
      expression: 0 0 0 ? * *

This is reproducible on Data Center: yes

Steps to Reproduce

1. Create deployment with environment triggered by schedule
2. Use custom branch to be deployed from
3. Export deployment project configuration to YAML Specs

Expected Results

Branch is defined at cron trigger

Actual Results

Branch is not defined at cron trigger

Workaround

Use Java Specs