Add OAG branding to TanzLII

[NotoriousMBB]

Two outstanding areas for OAG branding

add logo of OAG here

and in the footer - link to OAG website.

Also change the blurb to
TanzLII is operated by the Judiciary of Tanzania and the Office of the Attorney General, Chief Parliamentary Draftsman, and publishes the law of Tanzania for free online access for all. Free Access to the law supports the rule of law and access to justice. TanzLII partners with African Legal Information Institute (AfricanLII) and Laws.Africa NPO, who provide it with technical support.