cleanup spring 5 pom (#2700)

* fix spring config

* fix spring config

* fix spring config

* minor fix

* fix spring-boot module

* fix pom

* upgrade jackson

* minor fix

* java concurrency

* cleanup

* fix conflict

* java 8

* clean up

* add core-java-8 to main pom

* rename kotlin to core-kotlin

* update spring 5

* cleanup pom

spring-5-mvc/pom.xml

@@ -14,7 +14,7 @@
     <parent>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-parent</artifactId>
-        <version>2.0.0.M1</version>
+        <version>2.0.0.M3</version>
         <relativePath/>
         <!-- lookup parent from repository -->
     </parent>
@@ -165,14 +165,6 @@
     </build>
 
     <repositories>
-        <repository>
-            <id>spring-snapshots</id>
-            <name>Spring Snapshots</name>
-            <url>https://repo.spring.io/snapshot</url>
-            <snapshots>
-                <enabled>true</enabled>
-            </snapshots>
-        </repository>
         <repository>
             <id>spring-milestones</id>
             <name>Spring Milestones</name>
@@ -183,14 +175,6 @@
         </repository>
     </repositories>
     <pluginRepositories>
-        <pluginRepository>
-            <id>spring-snapshots</id>
-            <name>Spring Snapshots</name>
-            <url>https://repo.spring.io/snapshot</url>
-            <snapshots>
-                <enabled>true</enabled>
-            </snapshots>
-        </pluginRepository>
         <pluginRepository>
             <id>spring-milestones</id>
             <name>Spring Milestones</name>