make code signing optional in build

Author: UnquietCode

build.gradle

@@ -32,11 +32,11 @@ uploadArchives {
 beforeDeployment { MavenDeployment deployment -> signing.signPom(deployment) }
 
 repository(url: "https://oss.sonatype.org/service/local/staging/deploy/maven2/") {
-authentication(userName: ossrhUsername, password: ossrhPassword)
+authentication(userName: hasProperty('ossrhUsername') ? ossrhUsername : '', password: hasProperty('ossrhPassword') ? ossrhPassword : '')
 }
 
 snapshotRepository(url: "https://oss.sonatype.org/content/repositories/snapshots/") {
-authentication(userName: ossrhUsername, password: ossrhPassword)
+authentication(userName: hasProperty('ossrhUsername') ? ossrhUsername : '', password: hasProperty('ossrhPassword') ? ossrhPassword : '')
 }
 
 pom.project {