[MlMt] Change default "from" email address behaviour

[vincent at acheson.uk.com]

@Sherif - Thanks for the suggestion - that has been my latest attempt to 
overcome whatever the (dumb) perception / UI /lack of attention to 
detail issue I have….. much helped by using the following excellent 
hidden preference

> defaults write com.freron.MailMate MmComposerInitialFocus -string 
> "alwaysTextView"

@Benny - looks promising! It’s a shame that your excellent design idea 
doesn’t work for every user! I will try to remember to report 
back…..

Vincent