Simplify dependency management

Use dependencyManagement for versioning shared dependencies
Use pluginManagement for versioning and configuring plugins

api/pom.xml

@@ -19,23 +19,29 @@
   <modelVersion>4.0.0</modelVersion>
 
   <parent>
-    <groupId>com.lishid</groupId>
     <artifactId>openinvparent</artifactId>
+    <groupId>com.lishid</groupId>
     <version>4.1.7-SNAPSHOT</version>
   </parent>
 
   <artifactId>openinvapi</artifactId>
   <name>OpenInvAPI</name>
 
+  <dependencies>
+    <dependency>
+      <artifactId>annotations</artifactId>
+      <groupId>org.jetbrains</groupId>
+    </dependency>
+    <dependency>
+      <artifactId>spigot-api</artifactId>
+      <groupId>org.spigotmc</groupId>
+    </dependency>
+  </dependencies>
+
   <build>
     <plugins>
       <plugin>
         <artifactId>maven-compiler-plugin</artifactId>
-        <version>3.8.1</version>
-        <configuration>
-          <source>1.8</source>
-          <target>1.8</target>
-        </configuration>
       </plugin>
     </plugins>
   </build>