About page text, first pass.

Merges [30821] to the 4.1 branch.

props johnbillion, helen, markjaquith, nacin.
see #30435.


git-svn-id: https://develop.svn.wordpress.org/branches/4.1@30822 602fd350-edb4-49c9-b593-d223f7449a82
Rename `(get_)the_pagination()` to `(get_)the_posts_pagination()` for clarity.

Merges [30823] to the 4.1 branch

See #29808
Props obenland


git-svn-id: https://develop.svn.wordpress.org/branches/4.1@30825 602fd350-edb4-49c9-b593-d223f7449a82
Switch to `(get_)the_posts_pagination()` in Twenty Fifteen.

Merges [30824] to the 4.1 branch.

See #29808
Props obenland


git-svn-id: https://develop.svn.wordpress.org/branches/4.1@30826 602fd350-edb4-49c9-b593-d223f7449a82
4.1 RC1


git-svn-id: https://develop.svn.wordpress.org/branches/4.1@30827 602fd350-edb4-49c9-b593-d223f7449a82