make google-tracking-code optional

[Finkregh]

are ppl supposed to run this on their own? (then make the google-tracking-stuff mandatory/remove it from the "official" repo)

[ see https://github.com/bnolan/diaspora-x2/commit/368183fcfd10ff430d48d981ca74fd15364938aa#commitcomment-231984 ]

[thejh]

@bnolan, do you really want to track other people who visit other peoples installations of this?