Problem:
The user group permission checkboxes of Khronos are missing if CGCalendar is
installed at the same time.

What should happen:
Both, CGCalendar’s and Khronos’, user group permissions should be visible.

Steps to reproduce:
1. Install CMSMS
2. Install CGCalendar (with its dependencies CGExtensions and CGSimpleSmarty)
3. Install Khronos (with its dependencies CMSMSExtensions and SimpleSmarty)
4. Go to “Users > Backend Group Permissions“ → only CGCalendar permissions are
shown (but they affect both modules!)
5. Uninstall CGCalendar and look at permissions again: no respective permissions
are shown.
6: Uninstall and reinstall Khronos and look at permissions again: Khronos
permissions are shown
7: Reinstall CGCalendar and look at permissions again: only Khronos permissions
are shown

So, it seems like only the permissions of the module that was installed first
are shown. But setting these permissions affect both modules.