JSON-RPC

Changes made in this pull-request:

- jsonrpc api with all methods available from javascript-api
- added cors headers to jsonrpc
- separated libethrpc
- Javascript jsonrpc client, with the same interface as Javascript bindings in EthereumBrowser, so there is now possibility to run/debug code using eth object in Chrome/Firefox and other browsers
- here is a playground - https://github.com/debris/eth-client-example
- added async setters/getters for javascript properties
- tests for most of jsonrpc methods

* api is not yet unified with Go client api
Fixed in c2095d44b71149d99967f890dc5ddae576e30552 . clientDieing is now called when QWebView is deallocated