add UNDP logo to makemyisland cobrand, as per #863
change UNDP logo to top right as per client's instructions
use relative not absolute refs in layout SCSS
add explicit BASE_URL to URLs in nav and header, works in admin
use site_title in password titles (for makemyisland), part of #863
add site_title to the admin/config page
Merge branch 'master' into issues/863-makemyisland-changes