fix linking errors for Mac OS X, as far as dependencies are concerned
check for CLANG on OSX. If available, set the std++ lib so it solves the
final linking error coming from sfml actually (which uses std:
'sf::Font::loadFromFile(std::string const&)", referenced from:...')

This solves compiling and linking but generates lots of warnings
(most unused-parameter)
Minor formatting adjustment.
Added Stefan Hendriks to AUTHORS file.
Split Renderer into an interface and 2 instanciations using VBOs and vertex arrays, fixed corner case bug with Canvas, fixed viewports not propagating properly, fixed index count not being reduced in renderer when Primitives are removed.
Generalized Renderer textured quad creation from CreateImage into CreateSprite allowing Engine developers more freedom to manage resources and convey their usage.
Fixed FindSFGUI.cmake ignoring standard arguments (applied patch from #674), removed obsolete UpdateViewRect() from sfg::Desktop (#682), allow creation of RadioButtonGroups in advance (#685).
Fixed Renderer crashing when drawing without any textures loaded into the atlas by forcing creation of the pseudo texture by the Renderer during its construction.
Fixed loading fonts in renderer (#701, patch by Dematos).
Minor formatting adjustment.
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.