Add build date to startup info & plugin.yml, thankyou to paid users, more information to premium jar file check and expose more buyer information for the unseen future

pom.xml

@@ -36,6 +36,8 @@
 
     <properties>
         <build.number>unknown</build.number>
+        <timestamp>${maven.build.timestamp}</timestamp>
+        <maven.build.timestamp.format>dd/MM/yyyy HH:mm</maven.build.timestamp.format>
         <maven.compiler.source>1.8</maven.compiler.source>
         <maven.compiler.target>1.8</maven.compiler.target>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>