remove off-brand osgeo foundation and initiative icons

[jodygarnett]

The font has several "foundation and Initiatives icons" that are off brand:

• official foundation committees make use of osgeo mark as per style guidelines
• geoforall is a joint-initiative has uses slightly different colors

See #206 for discussion

[jodygarnett]

We should probably move this from:

• https://github.com/OSGeo/osgeo/tree/master/marketing/branding/symbols

To:

• https://github.com/OSGeo/osgeo/tree/master/marketing/symbols

Because the symbols are a derived product and not part of the branding.

[jodygarnett]

And remove the ".DS_Store" hidden files.

[jodygarnett]

@nbozon see above

[sidhansu10]

@jodygarnett,
It looks like PR #253 addressed the file moves and cleanup described in this issue. Unless there are remaining branding concerns, this issue may be ready to be closed.