Allow countries to customize activity ordering.

[cscott]

The attached patch to activitytray.py allows countries to customize the order in which activities show up in the build by creating an /home/olpc/Activities/.defaults file. This requires no changes to the customization key.

This is a feature requested by our deployment countries (Peru, Mexico) for update.1. The patch is small, and even in the worst case should not cause sugar to fail (we'll just display activities in a random order).

[cscott]

Patch to activitiestray to check a custom activity ordering file in /home/olpc/Activities.

[mstone]

The patch looks like a conservative extension of the existing functionality and I think we're fine using it as is (assuming it works). However, from the broader stability standpoint, do we really want Sugar to blow up if it can't find any readable activity.defaults files?

[cscott]

I was just extending the current behavior. But one could easily wrap another try/except block around the second 'read_one' if you wanted to protect against poor builds.

[marco]

Checked in with some modifications. It will go in next joyride.

[marco]

I forgot to mention that this went only on the update.1 branch. Activity management is going to change heavily with the redesign and tomeu already have code which conflicts with this.

[erikos]

Tested as working in 1758.

[erikos]

Is working fine in Update.1(700)