Modified "ToZerobraneStudioHook.lua" to require "ToDoxHook.lua" for avoiding code repetition.
Added Urho3D's License in Lua files.
Also update credit info in the Doxygen page. [ci skip]
Merge branch 'master' of github.com:silverkorn/Urho3D.
For Travis CI - use 'travis_retry' command to improve the odd.
See https://github.com/travis-ci/travis-ci/issues/2000.
[ci skip]
Merge remote-tracking branch 'upstream/master'

Conflicts:
	Source/Engine/LuaScript/pkgs/ToCppHook.lua
	Source/Engine/LuaScript/pkgs/ToDoxHook.lua
	Source/Engine/LuaScript/pkgs/ToZerobraneStudioHook.lua