ENYO-2723: DO NOT MERGE (wait for merging https://github.com/enyojs/ares-project/pull/389 first) the iconButton related to a relative path in projectProperties indicates if the path is valid or not (top file path currently)

Related JIRA: https://enyojs.atlassian.net/browse/ENYO-2723

* In any specific project related properties, the "Top File" relative path for the "Preview" has an "iconButton" to trigger its update. This button now indicates if the path is valid or not.
* Continuous improvement: 
 * Image licence: https://enyojs.atlassian.net/browse/ENYO-2726
Checked on Windows 7 : Chrome

DO NOT MERGE (wait for merging https://github.com/enyojs/ares-project/pull/389 first)

Enyo-DCO-1.1-Signed-off-by: Vincent HERILIER vincent.herilier@hp.com