removed default "no sessions found" message from course manager page template. refs #203
added new course loading indicator label to language files.
refs #203
added "loading all course sessions" status indicator to course manager. separated sessions toolbar visibility handling from the status indicator container to provide earlier/better loading status feedback to the user. fixes #203
refactored generateProgressDivMarkup(): pulled message out into a method argument. added docblock.
shuffled things around to show "loading course details" message early on.
added a line to clear the status progress bar after the course tree has been loaded.
Merge pull request #233 from stopfstedt/bug203

fixes #203