Introduce code node & get rid of code map (#398)

* introduce code node

* replace codeMap with code touches

* fix a comment

* fixups to tests

* fix compile error

* fix getnodedata tests

* add tests and test stubs

* add more test stubs

* add test method bodies

* add and fix more tests on trie for new codenode

* add test change code between blocks

* fix crash in stateless

* remove unneded files

* remove comment

* fix deleted account code

* fix resolve set builder for code nodes