Always load libraries using actualfile().

Otherwise, add-password and rm-password will crash if they are symlinked
into the user's PATH (rather than PATH modified to include
password-vault's bin dir).
Don't crash clients if TO_EMAIL and FROM_EMAIL unconfigured.
Improve {add,rm}-password usage string.

We really don't want users to be naming things after the actual password
itself. This change makes it clear that passwords should be named after
the services they are for, and that the contents of the encrypted file
are entered later.
Merge pull request #1 from spang/master

Always load libraries using actualfile().