Divert a river through the Augean Stables that is SpecialBlockip.php.

Divert a river through the Augean Stables that is SpecialBlockip.php.
* Move to SpecialBlock.php, and rename class appropriately
* Complete refactor
* Use HTMLForm in block form.  This changes most of the ids and field names on the form, but allows proper validation, nicer formatting, clears up several fixmes, and is generally Better(TM).
* Spin various parts out into static functions, several of which properly belong in the backend (but Block.php is a worse mess still)
* Invert some of the block options so that every checkbox makes the block more severe (so "check to disable email" is fine, but "check to allow usertalk edit" (default true) is inverted to "check to disable usertalk edit" (default false).
* revert r40359 (move doMassUserBlock() to core).  No one seems to be using this function, which has nothing to do with the frontend UI in SpecialBlock (it might perhaps belong in Block.php); it is pretty bespoke for CheckUser, doesn't seem to have very much utility elsewhere.