[features] renaming process -> trove

This is because the name "process" is far too general (it could be anything)
and "trove" much better describes what it is we're interacting with.
[features] moving password-related code into password_file.py
[features] extracting duplicated encoding code into its own routine
[features] removing unused imports
[features] moving more password-file related code into password_file.py
[features] starting to move program startup steps together
[features] moving shutdown-related code into its own file