Add support for crypted passwords to password lookup

Added new parameter 'encrypt' with same semantics from that of
vars_prompt. When encryption is requested a random salt will be
generated and stored along the password in the form:
'<password> salt=<salt>'.

Also store passwords with an ending '\n' for easier looking at files
with console tools. File content was being already rstripped so this
is harmless.
Fix name in copyright
Merge pull request #2939 from mmoya/lookup-crypted-passwds

Add support for crypted passwords to password lookup