Add gradle task to update the plugin version (#126)

Author: gaiksaya

build.gradle

@@ -299,3 +299,14 @@ diffCoverageReport {
         failOnViolation = true
     }
 }
+
+// updateVersion: Task to auto update version to the next development iteration
+task updateVersion {
+    onlyIf { System.getProperty('newVersion') }
+    doLast {
+        ext.newVersion = System.getProperty('newVersion')
+        println "Setting version to ${newVersion}."
+         // String tokenization to support -SNAPSHOT
+        ant.replaceregexp(file:'build.gradle', match: '"opensearch.version", "\\d.*"', replace: '"opensearch.version", "' + newVersion.tokenize('-')[0] + '-SNAPSHOT"', flags:'g', byline:true)
+    }
+}