CSV importer and on screen response

This update includes a CSV importer which gathers the .csv files for
stimulus presentation either from the file pool (ideal) or the same
folder as the experiment file. File names must match this criteria:
'Color_stim.csv'
For example: 'Red_net2.csv' ; not 'red_net2.csv'. See 'inline_script'
for more details.
Also added visuals cues for which button corresponds to a match or
mismatch. Keyboard buttons were changed from left and right shift keys
to 'z' and 'm', so as to prevent further grievances with damned Sticky
Keys in Windows.