Remove the predefined "Users" role

JIRA 3.7 comes with a roles "Developers" and "Users" predefined, with the implication that these roles take the place of the default 'jira-developers' and 'jira-users' groups.

In practice, it turns out that migrating jira-users to "Users" is a really bad idea. Whereas 'developers' is normally a per-project concept, jira-users means "people able to access JIRA", and is inherently a system-wide concept that shouldn't be made per-project. For instance, new users are automatically added to 'jira-users', but not to the 'Users' role for each project.

In general, any system-wide classification (jira-users, jira-administrators) should not be converted to roles, and we should not suggest doing so by having a "Users" role predefined.