Add prefs, menu items & customizable template path

Hey Keith,

great package, thanks a lot!

I thought, I could help finetune some things. So, these commits just add (user-overridable) pref files, menu items & a command so the project_maker task can be triggered from inside the command palette.

I plan to add another pull request that implements a user-definable template dir, which would make use of the user settings file.

What do you think?

Thanks, Carsten