Updated links for homepage template

In relation to https://github.com/IATI/IATI-Websites/issues/133
[#135] Update sitemap link to ensure it works on all pages
Merge pull request #135 from IATI/SF-navigation-fix

Updates links for homepage template
[#134] Updates the banner message in the template

This needs checking properly as I'm guessing at my conditional
statements in the code
Adds missing endif tag
Merge pull request #136 from IATI/134-signposting-to-201

[#134] Updates the banner message in the template