* remove experimental for loop macro usage
* make implementation of several operations follow data structure
(recursive data -> recursive implementation)
* rename getSize -> bitsof to avoid bits vs bytes confusion
* fix potential 32-bit issue where asSignedWords cast to `int` even when
`uint64` was used as storage
* `hi` for signed ints now is signed - this replaces `asSignedWords` and
makes several int operations more natural
* fix bit size assert
* Refactor asSignedWords, kill 130+ lines
* Allow signed int initialization at compiletime.
* inline procs in uint_mul
* Fix an unfortunate shadowing in high(Int)
* Start on allowing compile-time stint. Works for Uint256
* remove and reorder initUintImpl, zero and one procs
* Fix assignation of uint64 to 2xuint32, remove unsafeConv and use const for base/radix
* assign_least_significant_words shouldn't implicitly capture result
* Simplify least significant words macros
