Update README.
Correct prj command in new

We should use the new command to make the new project.
Update list to use config file.

We have a different structure, we now use config files and directories so the
list command needs to be updated. This does that. We read the config file using
penlight. It has a variety of useful functions to make scripting with lua
easier.
Correct problems with start.

Start should not use _MGR_ACTIVE but instead _MGR_INFO. In addition, we are not
yet in a project so we cannot rely on the settings of some env variables. We
should set them ourself then work with them. Maybe this is a sign of a possible
refactoring to do, move all the env setup into it's own env script.