Convert project to Gradle

The pom.xml file is deleted in this patch so the patch will fail to
apply if there are changes made to it from upstream - thus notifying us
that changes were made.

paper-api/.gitignore

@@ -1,3 +1,5 @@
+.gradle/
+
 # Eclipse stuff
 /.classpath
 /.project
@@ -32,3 +34,7 @@
 *.ipr
 *.iws
 .idea/
+
+# vs code
+/.vscode
+/.factorypath