Modified GUI under user study, fix bugs in GUI and back stage

Modified:
GUI font and color in the client
Button picture into flat ones to fit the style of the entire software

Fixed:
Bug in "design" about file loading
Bug in backstage searching and blasting
Bug in uploading biobrick through "design" interface

Added:
"/Executable/EasyBbk-Windows.zip" - packaged file which contains the software that can run without java environment under windows. (The version under linux and mac os is coming soon)