Simplify RTSPermissions and remove Vault dependency.

This commit will make RTSPermissions check the built-in SuperPerms instead of Vault for permissions (permissions plugins should implement SuperPerms instead of Vault, anyways). Also, permission checks have been changed from something like this:
```java
public static boolean isModerator(Player player){
    if(ReportRTS.permission != null) return ReportRTS.permission.playerHas(player, "reportrts.mod");
    return player.hasPermission("reportrts.mod");
    }
```
to something like this:
```java
public static boolean isModerator(Player player){
    return hasPermission(player, "reportrts.mod")
}

This also adds a simple check to see if a player has a permission (and also send the player a message if they don't so `Message.parse` is not necessary in every permission check):
```java
public static boolean hasPermission(CommandSender sender, String permission){
    if(!sender.hasPermission(permission)){
        sender.sendMessage(Message.parse("generalPermissionError", permission));
    }
}
```

I don't know how exactly this will impact performance (it *may* be a bit slower since there are now more checks), but I can imagine the impact (if any) is minimal. Also, I'm assuming there's no more need for `ReportRTS.permission != null` since this moves towards SuperPerms (thus also removing the need for double code blocks for *both* SuperPerms and Vault).

Plus, it makes the code look somewhat cleaner. 

Finally, this commit removes the stray "canImport" check since import support was dropped anyways.