Enable code quality tools in gradle for all subprojects

Enables the execution of the code quality tools in the subprojects
and configures them in a central place.

build.gradle

@@ -18,16 +18,13 @@ allprojects {
 // Plugins for subprojects
 subprojects {
   apply plugin: 'application'
-}
-
-
-apply plugin: 'java-library'
-apply plugin: 'pmd'
   apply plugin: 'checkstyle'
+  apply plugin: 'pmd'
   apply plugin: 'com.github.spotbugs'
+}
 
 
-
+apply plugin: 'java-library'
 
 sourceCompatibility = "1.11"
 targetCompatibility = "1.11"
@@ -60,30 +57,6 @@ dependencies {
     // Use JUnit test framework
     testImplementation 'junit:junit:4.12'
 }
-
-pmd {
-  ruleSets = [] // Gradle requires to clean the rule sets first
-  ruleSetFiles = files("config/pmd.xml")
-  ignoreFailures = false
-  toolVersion = "6.7.0"
-}
-
-checkstyle {
-  configDir = file("config")
-  configFile = file("config/checkstyle.xml")
-  maxWarnings = 0
-  ignoreFailures = false
-  toolVersion = "8.12"
-}
-
-spotbugs {
-  excludeFilter = file("config/spotbugs-exclude-filter.xml")
-  reportLevel = "low"
-  effort = "max"
-  ignoreFailures = false
-  toolVersion = '3.1.7'
-}
-
 // Per default XML reports for SpotBugs are generated
 // Include this to generate HTML reports
 tasks.withType(com.github.spotbugs.SpotBugsTask) {
@@ -94,14 +67,8 @@ tasks.withType(com.github.spotbugs.SpotBugsTask) {
   }
 }
 
-task checkstyle {
-  group 'Quality Assurance'
-  description 'Run Checkstyle'
-
-  dependsOn 'checkstyleMain'
-  dependsOn 'checkstyleTest'
-}
-
+// Subprojects quality tools tasks
+subprojects {
   task pmd {
     group 'Quality Assurance'
     description 'Run PMD'
@@ -110,6 +77,14 @@ task pmd {
     dependsOn 'pmdTest'
   }
 
+  task checkstyle {
+    group 'Quality Assurance'
+    description 'Run Checkstyle'
+
+    dependsOn 'checkstyleMain'
+    dependsOn 'checkstyleTest'
+  }
+
   task spotbugs {
     group 'Quality Assurance'
     description 'Run SpotBugs'
@@ -117,6 +92,33 @@ task spotbugs {
     dependsOn 'spotbugsMain'
     dependsOn 'spotbugsTest'
   }
+}
+
+// Subprojects quality tools configuration
+subprojects {
+  pmd {
+    ruleSets = [] // Gradle requires to clean the rule sets first
+    ruleSetFiles = files("$rootProject.projectDir/config/pmd.xml")
+    ignoreFailures = false
+    toolVersion = "6.7.0"
+  }
+
+  checkstyle {
+    configDirectory = file("$rootProject.projectDir/config")
+    configFile = file("$rootProject.projectDir/config/checkstyle.xml")
+    maxWarnings = 0
+    ignoreFailures = false
+    toolVersion = "8.12"
+  }
+
+  spotbugs {
+    excludeFilter = file("$rootProject.projectDir/config/spotbugs-exclude-filter.xml")
+    reportLevel = "low"
+    effort = "max"
+    ignoreFailures = false
+    toolVersion = '3.1.7'
+  }
+}
 
 allprojects {
   eclipse {