[Java] Upgrade to Checkstyle 8.0.

Author: mjpt777

build.gradle

@@ -121,7 +121,7 @@ subprojects {
     [compileJava, compileTestJava]*.options*.encoding = 'UTF-8'
 
     dependencies {
-        checkstyle 'com.puppycrawl.tools:checkstyle:7.8.2'
+        checkstyle 'com.puppycrawl.tools:checkstyle:8.0'
         checkstyle 'com.github.sevntu.checkstyle:sevntu-checks:1.23.1'
 
         testCompile 'org.hamcrest:hamcrest-all:1.3'
@@ -132,7 +132,7 @@ subprojects {
 
     checkstyle {
         configFile = new File(rootDir, 'config/checkstyle/checkstyle.xml')
-        toolVersion = '7.8.2'
+        toolVersion = '8.0'
     }
 
     compileJava {