Drop support for kitkat; Bump minSdk to 21

This has been dead for a while already, remove the code and bump minSdk to a
version that actually works

Signed-off-by: Aayush Gupta <aayushgupta219@gmail.com>

app/src/main/java/com/aurora/extensions/Activity.kt

@@ -21,19 +21,10 @@ package com.aurora.extensions
 
 import android.app.Activity
 import android.content.Intent
-import android.os.Build
 import android.os.Bundle
 import androidx.appcompat.app.AppCompatActivity
 
 
-fun AppCompatActivity.close() {
-    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
-        finishAfterTransition()
-    } else {
-        finish()
-    }
-}
-
 fun AppCompatActivity.restart() {
     val intent = intent
     overridePendingTransition(0, 0)

app/src/main/java/com/aurora/extensions/Platform.kt

@@ -25,10 +25,6 @@ import android.os.Build
 import java.util.*
 
 
-fun isLAndAbove(): Boolean {
-    return Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP
-}
-
 fun isMAndAbove(): Boolean {
     return Build.VERSION.SDK_INT >= Build.VERSION_CODES.M
 }

app/src/main/java/com/aurora/extensions/ThemeEngine.kt

@@ -121,7 +121,7 @@ private fun AppCompatActivity.setLightConfigurationO() {
     if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
         setLightStatusBar()
         setLightNavigationBar()
-    } else if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
+    } else {
         window.statusBarColor = ColorUtils.setAlphaComponent(Color.BLACK, 120)
     }
 }