Checkstyle fixes and warnings.

Should get 'working' builds now.

config/checkstyle/checkstyle.xml

@@ -5,8 +5,9 @@
 <module name="Checker">
   <!-- Tabs are strictly banned -->
   <module name="FileTabCharacter"/>
-
+  <module name="SuppressWarningsFilter" />
   <module name="TreeWalker">
+    <module name="SuppressWarningsHolder" /> <!-- allows for @SuppressWarnings annotation -->
     <!-- Important basics -->
     <!-- <module name="PackageDeclaration"/> Unlikely that we would miss this in a PR -->
     <module name="OuterTypeFilename"/> <!-- TypeName -> TypeName.java -->

config/checkstyle/import-control.xml

@@ -53,6 +53,7 @@
       <allow pkg="org.lwjgl"/>
       <allow pkg="io.netty.buffer"/>
       <allow pkg="org.spongepowered.api" />
+      <allow pkg="com.mojang.brigadier" />
     </subpackage>
 
     <subpackage name="sponge">