Massive overhaul

- The project was restarted using Android Studio.
- Adoptive platform-specific widgets has been removed due to build issues with Android.
- Dual-licensed under the BSD-3-Clause license and UNLICENSE.

ios/Runner.xcodeproj/xcshareddata/xcschemes/Runner.xcscheme

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "1020"
+   LastUpgradeVersion = "1300"
    version = "1.3">
    <BuildAction
       parallelizeBuildables = "YES"
@@ -27,8 +27,6 @@
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
       shouldUseLaunchSchemeArgsEnv = "YES">
-      <Testables>
-      </Testables>
       <MacroExpansion>
          <BuildableReference
             BuildableIdentifier = "primary"
@@ -38,8 +36,8 @@
             ReferencedContainer = "container:Runner.xcodeproj">
          </BuildableReference>
       </MacroExpansion>
-      <AdditionalOptions>
-      </AdditionalOptions>
+      <Testables>
+      </Testables>
    </TestAction>
    <LaunchAction
       buildConfiguration = "Debug"
@@ -61,8 +59,6 @@
             ReferencedContainer = "container:Runner.xcodeproj">
          </BuildableReference>
       </BuildableProductRunnable>
-      <AdditionalOptions>
-      </AdditionalOptions>
    </LaunchAction>
    <ProfileAction
       buildConfiguration = "Profile"