HTML Search: Use sphinx's built in search template file

[Blendify]

Instead of using our own template uses sphinx's basic search.html instead.
This change is almost identical except for the new search page includes
a search box. As a result, the search box is hidden on the search page.

Close #998

[stsewd]

Looks good. Just one thing, we are missing the display_vcs_links var that is used here

sphinx_rtd_theme/sphinx_rtd_theme/breadcrumbs.html

Line 27 in 38752d4

{% set display_vcs_links = display_vcs_links if display_vcs_links is defined else True %}

I think we can just check if pagename is different from search here

sphinx_rtd_theme/sphinx_rtd_theme/breadcrumbs.html

Line 41 in 38752d4

{% if hasdoc(pagename) and display_vcs_links %}