activation keys - test fix
system groups - ui - allow user to change env/view for systems in a group

This commit contains changes to allow a user to navigate to
a system group and then 'edit' the environment/content view
for all systems in that group.

As part of the change, created env_content_view_selector.js, which
we may be able to leverage in other places in the UI where similar
behavior is used (e.g. activation key & system 'create').