[Trellis-developers] checklist for 0.5.0 release

[Shaddy]

These are the unfinished portions of trellis that need to be completed 
for 0.5.0 (if you remember any others, add them to the list)

- Admin: add tabs to all mods (all browsers and user and course info 
pages are complete)
- Admin: update all info mods with make_info_form layout function
- Certificates: complete cert info and create cert mods, add event to 
remind learners about expiring certs, add setting for cert renewal threshold
- Catalog permissions, settings, and errors, confirm all used 
permissions/errors exist and list available settings on settings page in 
system interface
- System: Add very basic upgrade functionality, needs to copy over 
updated files and upgrade databases
- Plugins: Add basic plugin functionality, test it out with a real 
plugin to confirm it works
- Courses: automatically create/remove items
- Change $template variable to $templater
- Improve add_filter method in utilities
- Admin: Complete package browser and reusable package browser