Add 'Add speech' button on the speaker page.

The button is to the right of the 'Speeches' title for all sizes of screen.
At the moment it's not well vertically aligned with the search box
when the text 'Add search' is all on one line.
better vertical alignment for new speaker_detail button
Replace actions menu on section page with buttons.
speaker_detail.html: add Edit button, remove Actions dropdown
section_detail.html: de-emphasise Edit and Subsection buttons