Make it possible to configure default pipeline from UI

[annavik]

Summary

In this PR we make it possible to configure default pipeline from UI.

List of Changes

• Make the setting possible to set from the project configuration form
• Show the value as the pre selected option when starting a new job
• Show a "Default" label in the pipeline table

Related Issues

Closes #924

Screenshots

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[mihow]

Wow thank you for the thorough implementation!! I love the the new Processing section under Settings. The [DEFAULT] tag, and the auto-selected default pipeline in both pipeline drop-downs! This brings a lot together!