Added initial support for impersonation added

Conflicts:

	portlet/exoadmin/src/main/java/org/exoplatform/organization/webui/component/UIListUsers.java
	portlet/exoadmin/src/main/resources/locale/portlet/exoadmin/OrganizationPortlet_en.properties
	portlet/exoadmin/src/main/webapp/groovy/admintoolbar/webui/component/UIStarToolBarPortlet.gtmpl
GTNPORTAL-3089 - added css files and impersonation icon
Minor fixes related to impersonation