[feature/fp-series-5] Working set support for File Provider

[felix-schwarz]

Description

• Add working set support to File Provider to fully support favorites and tags (WIP)
• Update app sources for Xcode 10.2 + ios-sdk updates

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

[CLAassistant]

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1 out of 2 committers have signed the CLA.

✅ hosy
❌ felix-schwarz
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