Cleans a lot of code and fixes several bugs

Fixes joining by sign click not working
Fixes negative numbers breaking variable parsing
Fixes many messages not displaying properly

pom.xml

@@ -9,7 +9,7 @@
         <plugin.version>${project.version}-${buildnumber}</plugin.version>
         <buildnumber/>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-        <spigot.api.version>1.18</spigot.api.version>
+        <spigot.api.version>1.20</spigot.api.version>
         <spigot.version>${spigot.api.version}.1-R0.1-SNAPSHOT</spigot.version>
     </properties>
     <repositories>