replace deprecated dependency configurations

Using api and implementation instead of the
deprecated compile configuration.

Update to Gradle 6.0.

build.gradle

@@ -55,7 +55,7 @@ ext {
  * The shared configuration for all sub-projects:
  */
 subprojects {
-	apply plugin: 'java'
+	apply plugin: 'java-library'
 	apply plugin: 'eclipse'
 	
 	compileJava.options.encoding = 'UTF-8'
@@ -87,7 +87,7 @@ subprojects {
 	
 	// dependencies that all sub-projects have 
 	dependencies {
-		testCompile group: 'org.testng', name: 'testng', version: '6.14.3'
+		testImplementation group: 'org.testng', name: 'testng', version: '6.14.3'
 	}
 	
    task eclipseSettings(type: Copy) {
@@ -117,5 +117,5 @@ subprojects {
 }
 
 wrapper {
-    gradleVersion = '6.0-rc-2'
+    gradleVersion = '6.0'
 }