Update headers of Reference pages to reflect "3.0"

[scotthmurray]

As 3.0 is finalized, before the final distribution is assembled, update the Reference pages template to refer to "3.0+" instead of "2.0+".

[scotthmurray]

Closing this, as it looks like @REAS already did this, to coordinate with the 3.0b1 release.

[REAS]

Oh, yes I did. Thank you for closing.

[scotthmurray]

That part was easy. Thank you. :)