Parse boolean keywords in Node Params to actual PHP booleans

The original problem was that when you say something like "param1=false" in the Params field for a Node, it gets converted to (string) 'false', which when doing a simple truth test, evaluates to (boolean) true.

By converting these when the params are parsed, it should save time for all developers so they don't all have to do the simple check for the 'false' case.

The numeric test was added because the boolean test I used would also convert 0 and 1 to booleans, which in the typical case is probably not what we want. Hex option is included, but the octal is not since filter_var doesn't seem to handle those correctly anyway. See the [comment](http://php.net/manual/en/language.types.integer.php#111523) on php.net manual.

Unit test cases are available in this PR, but have not been tested due to my inability to set up a proper testing platform. Advice in this area is appreciated.