Refactor: add userResourcePath() accessor to ICore.

Access to the users private resource path (derived from the
settings path) has been used in quite some places, so it's
worth moving it to the core interface centrally.

Reviewed-By: Thorbjorn Lindeijer

src/plugins/projectexplorer/session.cpp

@@ -985,7 +985,7 @@ QStringList SessionManager::sessions() const
 
 QString SessionManager::sessionNameToFileName(const QString &session)
 {
-    return QFileInfo(m_core->settings()->fileName()).path() + "/qtcreator/" + session + ".qws";
+    return m_core->userResourcePath() + '/' + session + ".qws";
 }
 
 void SessionManager::createAndLoadNewDefaultSession()