ENYO-2886: "project.json" existence is well checked when folder node have not been expanded

Related JIRA: https://enyojs.atlassian.net/browse/ENYO-2886

"project.json" file existence is now well checked when the project folder node has not been expanded first and when it already contains a project configuration file.

Checked on Windows 7 : Chrome

Enyo-DCO-1.1-Signed-off-by: Vincent HERILIER vincent.herilier@hp.com