The features added by this function are not used anywhere.

Fix #151

Address the use case of autoload path removal, which allows themes
and packages definitions to be unloaded from running fish session.

Fixes an issue with history between shell reloads via refresh function call.
As `exec` replaces the current process in a non-gently fashion, the
persistent history could be out of sync with the in-memory history.

Calling `history --save` before `exec` should force the shell to persist the
history before replacing the current process.

Instead of overwriting functions that use `exec fish` on test
environment, skip this call if the variable `CI` has been defined on the
running shell.

In order to support dependency between plugins a function called
`require` has been added.

Swap `prompt_segments` and `refresh` description.

This was actually trying to load PATHs that do not exist under $OMF_CONFIG
directory and sourcing files that did not exist.