Objective

I was recently exploreing Entities and stumbled on something strange. Entities::len (the field) has the comment Stores the number of free entities for [len](Entities::len), refering to the method. But that method says The count of currently allocated entities. Looking at the code, the field's comment is wrong, and the public len() is correct. Phew!

Solution

So, I was just going to fix the comment, so it didn't confuse anyone else, but as it turns out, we can just remove the field entirely. As a bonus, this saves some book keeping work too. We can just calculate it on the fly.

Also, add additional length methods and documentation for completeness. These new length methods might be useful debug tools in the future.