Performance improvements

Significant performance improvements

• Load images on background thread.
• Images downsampled at the displayed size to improve performance with high quality photos
• Substantially faster loading of notes and emails
• Add Deselect all action, display in bottom bar when all items selected
• Refine messages CVU for website screenshot requirements
• Bump dependency versions. Bump realm to latest version (10) with previous multithreading bug resolved
• Fix message highlighting bug