Changes to analysis code to plot performance/holds

Signed-off-by: Andrew McKinney <mckinney@neuro.duke.edu>
More dataLoad and plotHolds changes.

plotHolds(subjs) now a working function w/ legend and auto name/save, dataLoad has a floor of x=0 for lower SD value and plots the start of the reward window.

Signed-off-by: Andrew McKinney <mckinney@neuro.duke.edu>