Annotations of intertrial choices, cue_switch, and iti_switch

[alexpiet]

• Adds annotations of intertrial choices, cue switch and iti switch
• All annotations can be included with df_licks = annotate_licks(nwb)
• plot_interlick_interval() is a function for easily plotting interlick intervals
• update session scroller
  • Need to add a check for reward annotations, since right now we get an error
  • Adopt a general approach of "if the annotation is provided, we plot it"
  • intertrial_choice
• Add significant unit test overall. Achieve 100% coverage with separate tests for important cases
• Add annotations for "within session" (resolves annotations should add label for "within session" #24)

[alexpiet]

@rachelstephlee @hanhou @hagikent @ZhixiaoSu This is ready for review

[rachelstephlee]

looks good. thanks for the addition.