wfs tile -- no need to pass special args

[euzuro]

We used to have to pass special args here because the wfs tile constructor was accepting an array of urls.

It seems that is no longer the case, and so there's no real reason to send a null for url here -- it just makes the code more complicated.

I'll leave the

this.url = url; 

line in there because (see next patch) I am going to propose that the base Tile class shouldn't be dealing with a URL parameter at all (this this assignment will be necessary)

[euzuro]

just pass same 'arguments' to tile constructor -- they are the same

[sderle]

if it doesn't break tests, go ahead

[euzuro]

r3029

[crschmidt]

Brought up to 2.4 branch for RC2 with r3088