Remove create_button

[jdarwood007]

Description

Sources/Theme.php createButton()

A note exists that it was deprecated in 2.1. In 2.0 we added the ability to use a custom create button logic:

! Allow themes to use "template_create_button" to create their own buttons (Subs.php) [Bug 1878]

I searched the entire customize site, could not find not one reference to this.

I think we are safe to remove it.

[Sesquipedalian]

Agreed

[Sesquipedalian]

Like all things related to the theme, this belongs in the Alpha 3 milestone.