* core/state: abstracted "write account to trie" method

* fix appveyor build

* Apply suggestions from code review

Co-authored-by: Martin Holst Swende <martin@swende.se>

* review feedback

* core/state/accounts: move Account to core/types

* core/types: rename Account -> StateAccount

* core/state: restore EncodeRLP for stateObject

* core/types: add the missing file

* more review feedback

* more review feedback

Co-authored-by: Martin Holst Swende <martin@swende.se>
Co-authored-by: Felix Lange <fjl@twurst.com>