[#5083] - jsp pages refers to non-existing css resources

This was noticed with jasperserver-ce-3.7.1
A few JSP of jasperserver refers to css resources with wrong absolute path names.

I.E. apache-tomcat/webapps/jasperserver/WEB-INF/jsp/loginError.jsp
28: <LINK href="/stylesheets/styles.css" type="text/css" rel="stylesheet">
29: <LINK href="/stylesheets/base.css" type="text/css" rel="stylesheet">

This returns 404 errors and you get unpredictable behaviour if other services are present on the same server, or if accessing from behind a reverse proxy.

css should be properly referenced in jsp using ${pageContext.request.contextPath}

A quick grep points to the following files requiring to be escaped:
WEB-INF/jsp/repository/repositoryExplorer.jsp
WEB-INF/jsp/flowError.jsp
WEB-INF/jsp/loginError.jsp
WEB-INF/jsp/flowRemoveError.jsp
WEB-INF/jsp/accessDenied.jsp
WEB-INF/jsp/olap/flush.jsp