Merge branch 'release'
- Check system and prompt an error message, when source code compiled
  under a wrong os
- Create a new header file to store runtime flags
something new
fixed some little problems
fixed bugs in FileManager
Bugs in FileManager may cause application crash
the glew glt sgengine merged into one project
fixed bugs
user can create a blank file now
Reduce the size of project
Merge branch 'develop'
New feature, less size
demo deleted