Update build tools and dependencies

[naXa777]

Changes recap

• Update Gradle wrapper to the latest version 4.10.1
• Update Android SDK build tools to 27.0.3
• Change target Android SDK version to 27 (i.e. 8.1 Oreo)
• Update Support libraries to 27.1.1
• Find and repair code broken by this update:
  • Use R.drawable.abc_ic_ab_back_material instead of R.drawable.abc_ic_ab_back_mtrl_am_alpha (back arrow)
  • Move layout_fragment_container out of android.support.design.widget.AppBarLayout.
  • Layout anchors to CoordinatorLayout are forbidden: Use android:layout_gravity to position FAB in the bottom right corner.
  • List item layout height should be wrap_content. If it's match_parent a single item fills the whole screen height.
• Use implementation instead of compile for declaring dependencies
• Add Google repository to resolve dependencies
• Cleanup: fix Android Studio warnings in some layouts
• Fix compile-time error in com.example.avjindersinghsekhon.minimaltodo.TestStoreRetrieveData
• Fix error in Travis CI build It still fails, but for another reason. Please update the google-services.json file, it seems like Gradle build plugin upgrade requires a new format.

  * What went wrong: Execution failed for task ':app:processDebugGoogleServices'. > No matching client found for package name 'com.avjindersinghsekhon.minimaltodo'

• Keep Gradle and Android caches between CI builds