Basic conversion of existing codebase to C++11, converted all #ifdef to #if defined for consistency, a bit of refactoring and a few fixes for undiscovered bugs.
Adapted CMake configuration to the new SFML linking system, made CMake project generation less painful by providing a few guiding hints, got rid of SFML as an extlib (it didn't make sense anyway since users would have an existing copy of SFML somewhere else already).
C++11 and general code adjustments.

- Turned shared_ptr references into non-references.
- Minor code style adjustments.
- Used std::make_shared where possible.

Conflicts:
	src/SFGUI/ResourceManager.cpp
	src/SFGUI/ScrolledWindow.cpp
Visual C++ 12 fixes/workarounds.

- Removed copy ctor and assignment operator in Renderer to workaround Visual C++'s move behaviour.
- Got rid of VC12 conversion warning.
- Removed preprocessor condition in Signal.hpp by dropping copy ctor and assignment operator. Provided custom move ctor and move assignment operator for satisfying MSVC who does not like =default.
Adjusted CMake config file.

- Removed unrelated configuration options (SFML options).
- Reduced amount of branches (simplified).
- Less cache overwrites/hacks.
- Unobtrusive compiler flags.
- Removed LIBRARY_OUTPUT_PATH.
Removed copyright line, fixed doc install target, added configured version.
Updated changelog.