Merge pull request #6560 from dumganhar/v2

issue #4674: Removed third party libraries and large files, moved them to https://github.com/minggo/cocos2d-x-resources
Removes external/emscripten & angleproject  submodule
Removes external folder
Re-adds resources in cpp-tests and lua-tests, but removes some large
files. We need to reuse some resources when doing some tests.

Conflicts:
	.gitignore
Moved Resource files
Re-adds TestLua lua source files.
Adds download-deps.py
Adds external/config.json
Adds box2d and chipmunk source codes
updates version.json and update .gitignore
Adds fps_images.png
Updates Testcpp xcode project
Updates travis-script
comment fix for download url
[emscripten] TestCpp Makefile fix
4spaces -> tab for emscripten makefile
[nacl] Adds '-lbz2' for native client port
Uses libfreetype.so to link
Reverts cocos2dx/proj.nacl/cocos2dx.mk
Merge pull request #6606 from dumganhar/v2-external-libs

Adds download-deps.py for v2 branch