Feature #4977: Fix an issue of localManifest loading
Feature #4977: Support temporary file downloading and rename if succeed
Merge commit '12d121fd5fb6e3ac70c498e6c8264af99e1aab33' into lua-vm

Conflicts:
	extensions/assets-manager/Downloader.cpp
Feature #4977: Fix compilation issue when USE_THREAD_POOL equals 1
Feature #4977: Improve function definition
Merge pull request #47 from pandamicro/lua-vm

Feature #4977: Support temporary file downloading and rename if succeed
Feature #4977: Refactor API of AssetsManager
Feature #4977: Add UPDATE_FAILED event
Feature #4977: Add UPDATE_FAILED event in test case
Feature #4977: Refactor Downloader::prepareDownload
Feature #4977: Refactor Downloader::batchDownload with curl_multi_perform
Feature #4977: Make downloadProgressFunc friend of AssetsManager
Feature #4977: Use a new thread for batch download
Feature #4977: Improve batchDownload logic and walkthrough the new curl multi perform process
Feature #4977: Improve error handling with curl error code returned
Feature #4977: Add batchDownload finish notification
Feature #4977: Improve and secure error handling
Feature #4977: Add AssetsManager::getFailedAssets and updateAssets function
Feature #4977: Add path information to removeDirectory error message
Feature #4977: Improve updateAssets function