Additionally, also fix a bug when creating a window, where as if the
session name was the same as a window that already existed, it would
fail, accidentally using the window rather than the session at a target.
* `session` and `window` commands are now know as `load-session` and
`load-window` respectively, with aliases for their former names.
* Add short aliases for various commands.
* `help` and `completions` commands have been expanded with support for
aliases.
* `help` command has been expanded upon with brief docs for a few more
commands.
