upgrade/StarWarsForms-MvvmCross7

[saamerm]

• Migrated the StarWars forms apps to MvvmCross 7
• Migrated to AndroidX by Right clicking on the Android project and selecting "Migrate to AndroidX"
• Then updated all the nuget packages by right click on the Packages folder in the Solution explorer-> Update
• Upon building, it told me I was missing another Nuget package Xamarin.AndroidX.Legacy.Support.V4 and Xamarin.AndroidX.Browser, so I added those two as well
• The latest version of the Lottie package doesnt support a target framework less than Android 10, so I had to increase the target framework of the Android project
• Migrated the Core and iOS projects by simply right clicking the Packages folder and tapping on Update

Testing

• Tested on an Android 10 device and the Forms app built
• Tested on iPhone 8 simulator and it worked

Notes

• Tried to update the Traditional/Native Android project as well, but I got this error "Views/PersonView.cs(55,50,55,61): error CS7069: Reference to type 'MvxColor' claims it is defined in 'MvvmCross', but it could not be found"
• Also had issues updating the TipCalc sample
• Did not test UWP