Provide a more visual way to enable the PopCon participation

The Ubuntu Popularity contest is very useful to Ubuntu.

From: https://wiki.ubuntu.com/SimplePopconParticipation
"[It is] used for such purposes as determining which packages to include on Ubuntu CDs and sorting in package management UIs. However, choosing to participate in this program is cumbersome and should be simplified. The more users participate in this effort, the more useful the information is. However, participation cannot be enabled by default for privacy reasons. Thus, we would like to make it simple for the user to opt to participate."

The aim of popcon is to get a statistically unbiased representation of package usage. The current method of enabling popcon (https://help.ubuntu.com/community/PopularityContest), and proposed methods (hiding it in the preferences of software sources), essentially mean that popcon only gets data from advanced users. This skewness in the data renders the results of far less use as the sample is biased.

In order to obtain more "clean" data, each (administrative) user should have the same probability of enabling the application.

The logical method by which this aim could be achieved would be to ask the user the first time that Synaptic or Add/Remove is started (unless the user has already enabled it). This would ensure that only those with admin rights would be asked, would ensure that the privacy implications were properly explained but maximise the use of the project.

The message could read:
"<bold>Would you like to participate in the Ubuntu Popularity Contest?</bold>
The Ubuntu Popularity Contest is an easy way to assist the Ubuntu team. By sending us information about what you have installed, we can ensure that we are focusing on the programs that people use most! For more information, please visit: <url to help on popcon>
[x] Enable the Ubuntu Popularity Contest
[ ] Do not enable the Ubuntu Popularity Contest"