Add Alias BeforeMarketOpen Passthrough to AfterMarketOpen( period * -1)

[jaredbroad]

Expected Behavior

Add the intuitive "before market open" instead of requiring clients to enter negative numbers.

Actual Behavior

Only have support for after_market_open(-10)

Potential Solution

Implement wrapper pass-through scheduled event API. Also apply to the missing after market close* method

Checklist

• [x] I have completely filled out this template
• [x] I have confirmed that this issue exists on the current master branch
• [x] I have confirmed that this is not a duplicate issue by searching issues