[reports] Reports without experiments could be made a bit more user-friendly

Here is the cut and paste from the mailing list discussion:

JG: You go to the reports tab.
You create a new report.
You press on "add a new report item"
You press on figure/table
You press on results
Nothing happens and there is no way of exiting the screen except going backwards with the browser.

I understand this issue comes from the fact that no experiments have been "previously" added to the report. To add an experiment you have to go to that particular experiment and press "add to report".
From my point of view the user's experience would improve if:

- A button "add experiment" was included in the report (similar to the current button "add a report item"). So that you can add experiments directly from the report (instead of going back to the experiment)

- Also, if someone presses on "add a report item" before an experiment has been added to the report, it would be nice if a pop-up informed the user that: "you need to add an experiment to the report before you can add an item" (or something similar)

AA: The most effective way to implement this, IMO, would be to disable the button and have a static message, with an explanation, including a link back to the experiments page.

Adding an experiment through the report, though relatively easy to implement, would be limited in terms of information displayed (e.g. date and name) because of the pop-up size and the incredible amount of info a user may need to select one and not another.