added apiserver and api client implementation of change password.

Added the api server and client set password command

Added the change-password user command

Thing to consider: 
> SetPassword only lets you change the password of the currently logged in user. Should the api really force this or should the commands force this behaviour (but not allowing the user to be specified)

> The change-password command writes the new password back to the yaml. Maybe the new file should be output as well?
(I *really* don't want to force manual recovery ever, unless someone went and manually messed up the .jenv ;p. IMO dropped connections are normal enough that we should assume they'll happen and design around them.)