[Systems] change to activities.sugarlabs.org config

[David Farning]

I made a modifications to the a.sl.o config to prepare for mirrorbrain.

a.sl.o stored activity data in two places:

/srv/www-sugarlabs/activities/files
http://download.sugarlabs.org/sources/activities

These two locations were symlinked when in fact, they should be
separate.  The first location is the 'internal' tree and the second is
the 'download' tree.  All activities are stored in the internal tree.
Once an activity is made public it is pushed to the download tree.

A second reason for the difference is mirror delay.  a.sl.o is
currently set to server files from the internal tree for 30 minutes
after a activity is made public to give the mirror system a chance to
propagte before serving from the download tree.

I also moved http://download.sugarlabs.org/sources/activities
http://download.sugarlabs.org/activities

david