added upgrade gradle script

update_gradle_wrapper.sh

@@ -0,0 +1,47 @@
+#!/usr/bin/env bash
+
+# Copyright 2018 Nishant Srivastava
+# 
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+# 
+#    http://www.apache.org/licenses/LICENSE-2.0
+# 
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+# ______________________________________________________________________
+#  Call as
+#  ./update_gradle_wrapper.sh
+# ______________________________________________________________________
+
+read -p "  ❓  Update gradle wrapper to which version?   " version
+
+# Iterate over each child directory inside the current directory
+echo "      Updating gradle wrapper for:"
+# Iterate over each sub-directory inside the current directory
+for DIR in ./*;
+do
+	# Check if gradlew exists inside the $DIR directory
+	# If it does then it is an Gradle project
+	if [ -f "$DIR/android/gradlew" ]; then
+		# Navigate into the sub directory
+		cd "$DIR/android"
+
+		# Run command inside the sub-directory i.e Gradle project
+		./gradlew clean | egrep 'FAILED|WARNING' 
+		./gradlew wrapper --gradle-version $version --distribution-type all | grep "FAILED"
+
+		# Print the name of the sub directory when done
+		echo "$DIR" | awk -F'/' '{print $2}' | xargs -I{} echo "      ↪️  {} ✔️"
+
+		# Go back to parent directory
+		cd ../../
+	fi
+done
+
+# Delete all generated build folders, because they will eat up a lot of space on the disc
+./delete_build_folder.sh