cmake dependency refactoring / windows build

### This will significantly change the build system

**changes**
* removed ./windows directory
* it is not possible to generate *msvc 2013* project from cmake
* cmake files refactored
  * cmake policies warnings are suppressed
  * removed EthDeprecatedDependencies.cmake
  * unified finding *boost* && *qt* libraries across all platforms
  * cmake script for finding XXX librariy moved to FindXXX.cmake
* it is now possible to download precompiled dependencies on windows
* *json-rpc-cpp* version upgraded *0.2.1 -> 0.3.2*
* removed mingw support on windows
* minimum cmake version upgraded to *2.8.12*
* fixed [static initializtion order fiasco](http://www.parashift.com/c++-faq/static-init-order.html)

**not yet finished**
* on windows, precompiled dependencies are built only in *win32* mode
* msvc project generated from cmake is only compiling in *'release'* mode.
* mscv does not copy required dll's to install directory
* downloading precompiled dependencies on other platforms (unix/mac), if required.
* cmake scripts compiling external dependencies from scratch on windows, (it would be usefull for upgrading external dependencies)

**possible future improvements**
* upgrade *json-rpc-cpp* to *0.4.1* (if required)
* mingw support
* support for older msvc versions (not only 2013)
* support for older WindowsSDK versions (not only 8.1)
* windows application installer

**questions**
* can *libethereumx*, *libpyserpent* be removed?
* can *QmlEthereum.h/cpp* be removed?
* can *walleth*, *iethxi* be removed?

Remove and/or output something informative if boost exception diagnostic isn't working. Also ought to create an issue to look into formally ensuring we can use same exceptions for windows. (see also, line 107)