Clarify presidential pseudovotes

[adamboche]

Currently the roll call pages include presidential pseudovotes in the vote tally, as do the data downloads. For example, this roll call has 119+1=120 yea votes. This is consistent with P & R's practice, but pretty surprising -- we get a lot of support emails about it.

• Change the display on the website to break up the 120 into 119+1=120 with an explainer message.
• Somehow clarify this in the data downloads. Perhaps emphasizing pseudovotes in the documentation or even adding a pseudovote column to indicate whether one of the votes is by the president.