Merge branch 'release/v5.2.1'

Change main buttons to responsive ones
Collapse main navigation for sm size as well
Remove unused files
Fix front page links
Fix links in footer
Fix links in header.php
Make page-subscribe look good
Add page-volunteer
Fix event table width issue
Add page-program
Add page-events
Add page-media
Add page-about-us
Add page-contact-us
Remove sidebar-about-us
Add link to partners page in footer
Make default page look nicer
Change screening template to page
Add customized Donate page
Improve responsiveness of main navigation
Hotfix: Remove resp buttons in md, lg sizes
Fix header line height
Hotfix: Remove resp buttons in md, lg sizes
Fix header line height
Fix event page links
Convert brochure into pdf file with two images
Fix Resources page template
Add background image to body