Results 3 issues of scidec

Add batch methods for end of day prices, splits and dividends. Update 429 retry policy. Include detailed exception that is returned to caller when something goes wrong.

Add sqr function as an overload of power. Remove debug assets to improve performance.

Add nullable dates to date from and to for historical dividends. I created a pull request for this before but it has been missed. Also update change_p case in extended...