Replaced Pools with Filters

Filters allow for a Pool constructor (defaults to Lists) that can be used to define Custom Pools.

The constructor is a function that takes the Filter Definition and returns a Custom Pool with these functions:

:add(e) - Add the Entity to the pool
:remove(e) - Remove the Entity from the pool
:has(e) boolean - Checks if the Entity exists in the pool
:clear() - Clears the Pool from Entities

Fixes #40

.gitignore

@@ -37,4 +37,7 @@ luac.out
 *.app
 *.i*86
 *.x86_64
-*.hex
+*.hex
+
+# VSCode
+.vscode/