Implement possibility to write plugins in other languages, then C++

[gropox]

In order to simplify developing of the plugins, could be nice to add posibility to write code in other languages, then C++.

Posibilities are

Javascript (preffered, because some developers around using it, json is native for javascript and used for communication)
https://github.com/v8/v8/wiki/Getting-Started-with-Embedding

Lua
http://lua-users.org/wiki/BindingCodeToLua

As first step, could be possible to pass operation just as json (no need to descriibe all operations as javascript objects, translation as json already implemented through reflection), and access to the database and block_log objects.

Optional, enable the possibility to add own api methods.

[kotbegemot]

#425