many changes

• background refresh implemented for Watch complications and app (IMPORTANT: complication data will never be real-time, all of the time)
• watch complication data is now disabled by default. Can only be enabled by going to the iOS app Settings -> Apple Watch and agreeing that the values will not always be real-time and should not be used for treatment decisions
• new "Contact Image" feature to automatically create and update a contact (with the app name) and a profile photo showing the current BG value and trend. If the contact image is disabled, the contact is automatically removed from Contacts. Add to the Apple Watch as a Contact complication and choose the app name. [@yurique, @callms]
• Siri integration to show BG and glucose chart when Siri is asked "What is my blood glucose". Add by going to the Shortcuts app on the iPhone, choose to add the app and add a phrase that you'd like to use. Several Siri Shortcuts can be added with different phrases as needed. [@gshaviv]
• changes to Live Activity views to make it clearer when BG is not current and also to unify colours across the new widgets
  log/tracing updates/corrections
• Watch app, Watch Complications and new Settings strings are localised into EN, NL, ES, DE and FR
• Developer Settings are now hidden by default. Enabling them will show them temporarily to allow adjustments.
• the legacy chart y-axis of 50, 100, 150, 200 etc is now removed from the app. Y-axis objective values is now always used.
• some settings are removed from Settings to declutter. "Show Target" is now removed and showing the target line can be enabled by entering a BG value in "Target" or disabled by entering "0". The UI is updated to will reflect this.
• placeholder data is now added to all widgets and complications to show what the chart will actually look like when selecting them (previously just showed a single glucose reading
• Data Management section removed from Settings as it doesn't currently really do much without a data import function. (Only commented out in view controller, can be re-added easily)
• Settings screen is updated with icons for each section to try and help users navigate more quickly