Streamline Gradle build scripts: using the Spring Dependency Management Plugin to manage dependencies and versions

Closes gh-21

Author: rainboyan

examples/grace-hibernate5-mongodb/build.gradle

@@ -1,5 +1,3 @@
-group = "examples"
-
 dependencies {
     implementation "org.springframework.boot:spring-boot-starter-logging"
     implementation "org.springframework.boot:spring-boot-autoconfigure"

examples/grace-mongodb-database-per-tenant/build.gradle

@@ -1,5 +1,3 @@
-group = "examples"
-
 dependencies {
     implementation "org.springframework.boot:spring-boot-starter-logging"
     implementation "org.springframework.boot:spring-boot-autoconfigure"

examples/grace-mongodb/build.gradle

@@ -1,5 +1,3 @@
-group = "examples"
-
 dependencies {
     implementation "org.springframework.boot:spring-boot-starter-logging"
     implementation "org.springframework.boot:spring-boot-autoconfigure"

examples/springboot-mongodb/build.gradle

@@ -1,12 +1,7 @@
-apply plugin: 'org.springframework.boot'
-apply plugin: 'io.spring.dependency-management'
-
-group = 'example'
-
 dependencies {
     implementation "org.springframework.boot:spring-boot-starter-web"
     implementation project(":grace-plugin")
 
     testImplementation"org.springframework.boot:spring-boot-starter-test"
-    testImplementation"org.spockframework:spock-core:$spockVersion"
+    testImplementation"org.spockframework:spock-core"
 }