web: Use HTML ids of image/container ids for locating container rows

These should be unique enough for us to use them directly. This
allows us to highlight them using jQuery straight from unrelated
code like the graph plotting code.

Signed-off-by: Marius Vollmer <mvollmer@redhat.com>
web: Return the element we're going to plot in

So that we can use it to catch events and stuff.

Signed-off-by: Marius Vollmer <mvollmer@redhat.com>
web: Add 'highlight' CSS class.

Signed-off-by: Stef Walter <stefw@redhat.com>
web: Highlight container rows when hovering over the graphs.

Closes #360

Signed-off-by: Stef Walter <stefw@redhat.com>