Improve visual behavior training procedure description

[matchings]

• Add more detailed / better organized description of session types
• add flash omit probability to table of task params per training stage
• add “with omissions” label to schematic of training stages
• add example code to get # sessions to criterion prior to recording sessions (i.e. what is the first session where mice are considered “well trained” in final stage of task)
• make it more clear what “handoff ready” and “handoff lapsed” mean
• add example code to aggregate task parameters across sessions
• add example code to aggregate behavior metrics across sessions (session level metrics and rolling performance df)
• add better description of reward rate and why it can be used to identify engaged / disengaged states
• add page of references for relevant papers and embed in data descriptions as appropriate
• add code to produce lick rasters