Slow graph tool when too many assets.

[CaoF]

1. 'AssetDatabase.Refresh()' needless in SaveData.Save(). Because json file read or write from file stream. Dose not using AssetDatabase.

2. 'Create Loader' is very slow first time(each create times). If target folder is ignore root(/Assets) get in 'IntegratedGUILoader.Load(...)' more fast.

3. 'NodeGUIEditor.DoInspectorLoaderGUI(...)' is problem. Load path input each times 'RecordUndoScope' and dispose but disposing call EVENT_SAVE and every times call SaveGraphWithReload(true). Only record on text field submit event avoid this problem.

[Sam Narain]

@CaoF currently for the 1.1, there are planned optimizations which include solving issue #2. Also, I partially agree to refresh AssetDatabase inside the saving mechanism. I assume that the saving mechanism will go through some modifications and optimizations in 1.1.

[Hiroki Omae]

In v1.1 there is a major performance improvement including solving some of the proposed ideas. I would like you to try out 1.1 and let me know if it is good.