[sugar] host_version

[Morgan Collett]

On the subject of activity.info,
http://wiki.laptop.org/go/Activity_bundles#.info_File_Format has this
to say about the host_version field:

Each activity.info file must have a "host_version" key. The version is
a single positive integer. This specifies the version of the Sugar
environment which the activity is compatible with. (fixme: need to
specify sugar versions somewhere. Obviously we start with 1.)

I checked activities I have in jhbuild and checked out from git, and
of the selection I have, only the following have host_version:

./chat-activity/activity/activity.info:host_version = 1
./etoys/activity.info:host_version = 1
./video-chat-activity/activity/activity.info:host_version = 2
./colors/activity/activity.info:host_version = 1

So this field seems to be generally unused, despite the requirement
above, and not used consistently - well, it's not even defined.

We now have other mechanisms to influence the activity updater, so
should this field not be deprecated?

Regards
Morgan