Updated to be compatible with Android 26 or higher without need of java.util.Calendar

[jlurena]

• Removed java.util.Calendar Dependency
• Removed Support Library Dependencies
• Updated build tools
• Updated Target SDK to 28, Android P

NOTE I do not want to merge into Develop (if its the main branch). I would just like a branch that can be driven by the community for Applications that only support Android 26 or higher, without the need of Support Libraries etc.

[AndroidDeveloperLB]

Really wish you had tried to work on my fork instead, as I've converted it to Kotlin, fixed a lot of issues, and added a few more features:
https://github.com/AndroidDeveloperLB/Android-Week-View

But according to what I see on your changes, you've raised the minSdk quite a lot. API 26 is only available to 5.7% of users out there, according to Android dashboard website:
https://developer.android.com/about/dashboards/

I would suggest other types of optimizations instead. One of them is to try to reduce number of instance creations of all classes upon drawing of the View, especially instances of Calendar class.