"Change Permalinks" button shows up when page is on front

[simonwheatley]

When a page is set as the front page, the "Change Permalinks" link shows up erroneously (normally this should only happen if the permalink scheme is undefined or does not contain %pagename% or %postname%).

The attached patch prevents the link from showing if the page being edited is the front page.

[simonwheatley]

Adds a check to see whether the page being edited is the front page before showing the "Change Permalinks" link

[azaozz]

(In [11908]) Don't show "Change Permalinks" button when editing the page set as "Front page", props simonwheatley, fixes #10760