Portals; Logos; Better support for SVG files

SVG files (Scalable Vector Graphics) are far superior to bitmap formats such as GIF or PNG for displaying graphics such as company logos.

On the Portals form, Theme page, 4 logos can be specified. These were originally geared towards bitmap graphics however, SVG works fine.

Sites such as https://www.fffuel.co/eeencode/ can encode SVG files that can then be pasted into the fields.

Encoded files are in the following format:

data:image/svg+xml;base64,PHN2ZyB4bWx...

Previously, importing files via the button to the right of the URL fields did not work correctly with SVG files. This has been remedied; SVG files can now be imported just like any other file.