Small UX improvements

[morteako]

• Hotkeys - f.ex. space => start/stop, w => workout editor, p => power controls?, h => heart rate connect , t => trainer connect
• Combine workout controls + power controls . Can keep both buttons
• Make it easy to hide parts of the UI, such as timers. Can just be toggled in the settings
• Fix "bug" that resets power to 0 when starting session.
• Add "reset session" button in the controllers to reset time distance workout, but keep BT connections