Interactive subj_trial_count_session_duration graph on reports page

[k1o0]

The subj_trial_count_session_duration graph plots trial count and session duration against session date for each subject. This information is in the sessions table of Alyx and can therefore be plotted interactively. A user has requested this so they can verify the precise values for each session.

[bimac]

@k1o0 to ask for a specific session where trial nums are wrong