Measures are continuous from below: general case (#2494)
Measures are continuous from below: general case (#2494)

* Limits for sequences of extended real numbers

* All new theorems have been minimized

* fixed comments as suggested by reviewer

* 4 lemmas renamed according to convention

* Measures are continuous from below: general case

* Changed comments for Lemmas, as suggested in #2479
metamath/set.mm,metamath/set.mm,metamath/set.mm