Less restrictive Funext_downward_closed

Funext has three universes, and we want them all to be independent; this
seems to be necessary to eliminate universe inconsistencies in the
latest version of trunk.
Use [apply path_forall], not [apply funext]
Don't have an extra universe in [pointwise_paths]

It's not necessary.  Removing it makes figuring out where universes in
Funext come from a bit easier.
Merge pull request #399 from JasonGross/more-general-funext-down

Less restrictive Funext_downward_closed
Merge pull request #400 from JasonGross/more-path-forall

Use [apply path_forall], not [apply funext]
Merge pull request #401 from JasonGross/less-pointwise-paths-universes

Don't have an extra universe in [pointwise_paths]