Updating translations (and fixed a few more issues with missing string replacements - upstream on LaunchPad.net). Also updating supporter list.

Cleaned up supporters.json file (I now have an automated script to generate this file, and it now removes lots of garbage)

Updating credits dialog to show PayPal, Kickstarter, and Bitcoin donations. Also, updating UI a bit (type-of-donation icons are collapsed into 1 column). Also updating supporters JSON file.

Added new Slice clip context menu. Did lots of work on the About screen (license, credits, formatting, etc...). Fixed bug with .settings file not writing to the .openshot_qt user folder. Fixed logger to write a log file to .openshot_qt. Fixed many context menus on the timeline (to respect the actual start values). Added properties context menu for clips, and improved the Simple and Advanced views.