Add a UK England and Wales holiday calendar
The rules are described at:
https://en.wikipedia.org/wiki/Public_holidays_in_the_United_Kingdom#England.2C_Northern_Ireland_and_Wales

Sample data used to check those rules (which is also included in tests)
is from the government's website: https://www.gov.uk/bank-holidays

I think the going assumption is that additional holiday calendars are supposed to be a separate package.  See #7070.  The existing ones are kind of there as an example more than the start of establishing a set of calendars that are in pandas.  
 I agree here. These could be in another package, but not in main pandas.
