standardize column name for auto reward across AllenSDK tables

[DowntonCrabby]

AllenSDK returns tables with a column called either "auto_reward" or "autoreward" The science team would like to have a consistent name.

Describe the solution you'd like
I'd like the naming to be consistent across all table column names and dictionary keys.

I personally prefer using "auto_reward" because the pkl file returns an 'auto_reward_volume' so we'd be keeping the naming consistent across both the SDK and the pkl file, but this is just a preference. I don't really care which naming convention is used it is as long as it's consistent within the SDK tables and dictionaries.

Additional context
SDK 2.7.0

The following attributes mention auto rewards:
trials
rewards
task_parameters (in the future, see ticket #1515 )

[wbwakeman]

Per Marina, change the field in the rewards table to 'auto_rewards'

[DowntonCrabby]

@djkapner is this going to be part of the next iteration of the sdk release?