Created new class OperatingSystem to set the GraphViz path base on the
type of Server OS and download paths based on the type of Client OS
CLUBUML-29: Fixed GraphVixPath issue for Mac,
			Fixed UploadServlet, DownloadDirectory Path issue for Mac
Fixed the issue of Download Single Diagram

Changed the OSDetails.setServerOS() and OSDetails.setGraphvizPath()
method to static Type
Adding gitignore for build folder
Not including build folder
Trying to rectify merge conflicts
Merge pull request #12 from ahajirnis/testMaster

Adding in Prasanna's changes