[webui] restructure branch dialogs

- Update 'Package > Branch package' dialog
    - Streamline information
    - Add Textfield for Branch destination project
    - Add Checkbox to disable OBS:AutoCleanup if
        AutoCleanup is enabled in OBS' config
- Update 'Project > Branch existing package' dialog
    - Streamline information

Changes of parameters passed require new cassettes.

Fixes #3656