Move group fixing logic

The group fixing behavior should be handled locally in case it is not desired
(planning on using insert_entry elsewhere).
Fix getopt errors

Stop printing my own errors when getopt will already handle all of it for me.
Turn INSTALL into symlink
Add more helper functions, fix copy references

This is an update to the helper functions before the new part that demanded
those changes in the first place.
Add mode for entries

Add a new mode for adding/removing/modifying entries. This should make
scripting password generation and maintenance a lot simpler.