Build system

Build-system with the corresponding Android/iOS/OS X toolchains cmake files, mainly architecture changes with new CMake build files. 

**Architecture changes**
- CMake : The project now uses CMake, inside the **build/** folder there are the toolchain and utilities cmake files. The first called and used CMake file is in the root **/CMakeLists.txt** and then runs the different platform-dependent cmake files, which then run the CMakeFiles of the dependent libraries if needed (like Core/GLFW/JSon/GLM). Added two toolchains file, one for android grabbed from [here](https://github.com/taka-no-me/android-cmake/blob/master/android.toolchain.cmake), and one for iOS grabbed from [here](https://code.google.com/p/ios-cmake/source/browse/toolchain/iOS.cmake); these files define all the pre-required variables in order to use CMake for the corresponding platform.
- Core : is now used as a static library, and has its own CMakeLists.txt.
- Json : is now used as a static library as a dependency of the Core static library.
- GLFW : is now used a a git submodule.
- Changed somehow the architecture of the project : iOS/OS X platforms has now an **src/** folder where to put the sources, an **include/** folder for dependency headers and a **lib/** folder to put libraries if needed.
- Removed old Makefile
- Further improvements/work : 
    + Use CMake to build the UnitTests 
    + It could be a good idea to modify a bit the CMake toolchain for Core in order to be able to generate an executable for it; for test purposes. 
    + Check which files are still needed inside the **android/** folder considering the new toolchain for this platform
    + GLM : could also be used as a submodule from [here](https://github.com/g-truc/glm)
    + Curl : use the same headers/static fat library for both OS X and iOS


**Source code changes**
- Fixed some missing inclusions 
- Fixed some compiler/standard library issues to fit for g++/clang++ at the same time
- Curl : used headers from [this project](http://seiryu.home.comcast.net/~seiryu/libcurl-ios.html)
Release configuration for Android is something we aren't quite set up for yet. The tool that builds the APK, ant, has a specific interpretation of 'debug' and 'release'. Debug builds are code-signed with a 'debug' key that only allows it to be installed on devices with debugging enabled. Release builds can be installed on any device, but require us to keep our own private key to sign the code. It's not too hard to set this up, but before we do it we should talk about how we want to manage code-signing as a company.