Added render options block to text review template.

Review Request #10731 — Created Sept. 29, 2019 and updated — Latest diff uploaded


Review Board


There is now a block in the text.html template that can be extended by
specific text review UIs that need custom render options, such as the ones
that will be used for the prettified XML and JSON viewers.

There is a div wrapping the block that will align the render options
to be consistent with the revision selector in the header.

1) Tested manually with the Markdown UI with a custom template to make sure
that options render nicely.
2) Tested manually with the Markdown UI with the default template to make sure
the layout looks the same as it did without this change.