SP-1158 - Backport of BISERVER-11010 - Administrator role does not show ...

...on Share tab for existing and new folders

What was done:
1) added field is modifiable to AceAcl DTO
2) changed ui to take care of the field
3) changed WS to ignore non-modifiable role and to add admin role for
display only

Conflicts:
	extensions/src/org/pentaho/platform/web/http/api/resources/FileResource.java
	user-console/source/org/pentaho/mantle/client/solutionbrowser/fileproperties/PermissionsPanel.java