Adding a block structure to the stimulus. Have multiple rounds (repeats)
of each block, which is a single condition. Each round is constructed to
have all transitions between conditions. Stimulus mostly works (sure to
be bugs later though). Moving on to stimdb additions.
Bug fixes and robustification of new basic-sens and blocked
temporal-sens stimuli. Renamed things more consistently, solidified
filtering, offloaded unique directory creation to another function.