* separate migration from util and make its dependencies into libs:

* snappy
* kvdb
* error
* common

* renamed common -> macros

* util error does not depend on snappy module

* ethsync does not depend on util nor ethcore_error

* nibbleslice and nibblevec merged with patricia_trie crate

* removed unused dependencies from util

* util journaldb traits does not need to be public

* util_error

* fixed ethcore compile error

* ignore .swo files

* Update chain.rs

* Rebase and fix compilation errors (tests not yet fixed)

* Use `debug_assert` over `assert`

* Fix tests

* Assert safety, clean up

* Fix up stale cache removal, move one assert to debug_assert

* Remove printlns

* Add licenses

* Fix benches

* Inline some no-ops in a hot loop that weren't being inlined

* Add spooky comment to make sure no-one removes the inlining annotations

* Minor cleanup

* Add option to switch between mmap and ram

* Flag ethash to use less memory when running light client

* Fix tests

* Remove todo comment (it's done)

* Replace assertion with error return

* Fix indentation

* Use union instead of `transmute`

* Fix benches

* Extract to constants

* Clean up and fix soundness holes

* Fix formatting

* Ignore missing-file errors

* Make incorrect cache size an error condition instead of a panic, remove dead code

* Fix compilation errors from rebase

* Fix compilation errors in tests

* Fix compilation errors in tests

* bytes
* hashdb
* memorydb
* nibbleslice
* nibblevec