Batch delete

Batch deletion option in action mode

Description

Allow to select & delete multiple media at once

Motivation and Context

Much asked feature, implementation is now simpler with Kotlin implementation thank to coroutines.

How Has This Been Tested?

Tested deletion on local storage on Oreo from fresh install. Same thing for external storage devices on Android 5+

Types of changes

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

Checklist

• I have read the CONTRIBUTING section of the README document.

Resolves

Fixes: #429 (closed)