Merge pull request #1 from zhangjn1991/private

New version with re-structured code and a bunch of new features:
- Folding of sub-graphs
- Search function
- Many UI improvements (zooming, repositioning etc.)
Renaming search file
removing search file
Adding Search file
Some clean up & slight modification of the layout
Resolve merge conflict
Merge branch 'pull-ready' of github.com:zhangjn1991/xdi-grapheditor into private-jingning
Refine find node functions
Add option to import a second graph without clear the screen
Add an option to add onto existing graph or build a separate graph
Merge remote-tracking branch 'upstream/master'