Reimplement thread pool

* Thread pool has been redesigned and rewritten
* Beter API has been provided (now supports C++11 functionals)
* Unit, stress and performance tests has been written.
Adjust core's code to new thread pool API

Verification: build all configurations, run tests, play with demo.
CRFIX

* TaskPtr -> TaskID
* style fixes
Merge branch 'devel' of github.com:nfprojects/nfengine into threadpool

Conflicts:
	nfEngine/nfCommon/nfCommon.vcxproj
	nfEngine/nfCommon/nfCommon.vcxproj.filters
	nfEngine/nfCommonTest/nfCommonTest.vcxproj
	nfEngine/nfCommonTest/nfCommonTest.vcxproj.filters
Merge branch 'devel' into threadpool

Conflicts:
	nfEngine/nfCommon/ThreadPool.cpp
	nfEngine/nfCommon/ThreadPool.hpp
	nfEngine/nfCommon/nfCommon.vcxproj
	nfEngine/nfCommon/nfCommon.vcxproj.filters
	nfEngine/nfCommonTest/ThreadPoolTest.cpp
	nfEngine/nfCommonTest/nfCommonTest.vcxproj
	nfEngine/nfCommonTest/nfCommonTest.vcxproj.filters
	nfEngine/nfCore/Engine.hpp
	nfEngine/nfCore/PhysicsWorld.hpp
	nfEngine/nfCore/ResourcesManager.hpp
	nfEngine/nfCore/SceneManager.hpp
[CRFIX]
Merge pull request #39 from nfprojects/threadpool

Refactor Threadpool class