[V7] usability: provide help tip for technical settings in res.users view

[Alexandre Fayolle - camptocamp]

In it's current state, the "Access rights" tab is hardly useable for end users with no access to the source code of open erp.

None of the options that can be checked have a description / help message attached, the names of the various options are not clear (how can a user guess that "Manage serial numbers" is related to the production of goods whereas "Manage logistic serial numbers" deal with serials in the reception / shipping of goods).

Proposed solution:

* the res.users view should use the "comment" column of res.groups to display a description of what the settings allows to do

* the various addons creating those res.groups should provide a detailed description of what the group allows to do in the comment column for the group.

Thanks for taking this in consideration.