Optional state overrides in RPC handler (#199)

* Sketch the basic structure

* optimize transaction count

* remove outdated todo

* update more comments

* Refactor to use existing RuntimeApi trait

* Delete commented code

* F we won't be able to re-use the runtimeAPI trait after all that.

* revert last three. Sharing the runtime API trait seems itwon't work. I guess to implement one runtime API my type must implement the core ones too.

* Comment summarizing why re-using the runtime trait won't work.

* Copy more functions from runtime api trait

* wip

* optimize gas price

* optimize balance

* optimize storage at

* optimize block by hash

* optimize block by number

* optimize block transaction counts

* optimize code at

* optimize transaction by *

* optimize transaction receipts

* wip

* match style for author

* rename to overrides

* Make author consistent with other methods

* need to think more carefully about the return types.

* Move trait and straighten out result types

* Migrate more functions. Close to compiling. Need to resolve option stuff.

* Fix options and some warnings

* remove override of gas price. Properly override author.

* don't override account_basic

* Remove outdated comment

* install optimization in node

* Add doc comment

* remove commented code

* Initilize the schema storage

* Simplify error handling. This seems less elegant, but it compiles.

* fix final test

* revert changes to tests

* restructure

* Start attempting well known key

* Fix confusing and aparently unrelated compile error

* Implement wrapper

* Install fallback and clean author method

* clean more methods

* clean more methods