DNN-3862 All page properties should be copied when copying a page
DNN-3865 Page settings do not save start date

Modified the logic in page management so when a page is copied a clone of previous page is use as the base for the new one.
Removed minimum value for start date so date is preserved when editing take place after start date
Merge commit 'c34d53f3beb185cdf33691a26f9cce31c1d0a1b1' into development