0.9.5 Double TrialBlocks per session

Updated so that users are prompted to take another TrialBlock after
their first on a single log in.  Should allow users to not take both at
once and login again at any time in the same day to take the 2nd one of
the day.  Should turn away users that have already taken 2 in the
current day or who haven't waited long enough since last session (Study
setting from admin).