Unify usage of prebuilt libraries in cmake builds.

* introduce config variable USE_PREBUILT_LIBS (default: ON). When OFF, cmake will not use prebuilt libs, only try find system installed libraries.
* FindGLFW3.cmake now search our prebuilt library (if USE_PREBULT_LIBS)
* FindFreetype.cmake also

This and next changes should simplify our CMakeLists.txt files and USE_PREBUILT_LIBS config allow external package developers to integrate cocos to their packaging system.
Unify WebP usage.
Fix WebP usage.

* Introduce config variable USE_WEBP (ON by default, but disabled for unsupported archs WINRT and WP8)
* Set CC_USE_WEBP define according to USE_WEBP variable
* add WebP include directories to search patch only for libcocos compilation (it not used in public headers)
Unify usage of chipmunk library

* cmake/Modules/FindChipmunk.cmake now can find prebuilt chipmunk libs
* follow USE_CHIPMUNK variable (although at the moment cocos can't build without chipmunk)
* come cleanups and formatting
Try to fix building without chipmunk, by define CC_USE_PHYSICS=0, but lua bindings still fail.
Improve FindFreetype.cmake for Mac
Unify TinyXML2 usage.

* should be included as simple "tinyxml2.h", but on some files was "tinyxml2/tinyxml2.h", replace this.
* Add cmake/Modules/FindTinyXML2.cmake
* As tinyxml2 for now has not prebuilt, instead sources included, add their as subdirectory if USE_PREBUILT_LIBS
Make FindTinyXML2.cmake use included macroses from same directory, as other our Find*.cmake modules
Unify Box2D usage and finding (not compilable, may be fix that later...)
Use COCOS_EXTERNAL_DIR in Find*.cmake modules
Compile Box2D tests only if library used in cocos.
Add custom FindJPEG.cmake module.
Find libpng and zlib unified way.
Fix building with system installed chipmunk on Mac. We should define CP_USE_CGPOINTS=0, or chipmunk will try use apple defined geometry types that conflicts with cocos types.
Find libtiff
Find libwebsockets in unified way
Add finding curl. Fix some leftovers from websockets.
Remove incorrect includes.
No sure about to remove comment, because it important, but work in this direction in progress now, so I remove it also.
Unify protobuf finding and usage.
But disable finding until bug with protobuf versions will be resolved.
Fix comments and formatting in FindTinyXML2.cmake