Making install script actually work correctly
Renaming .sample.env to .example.env
Adding MDF_WORK_TREE to .example.env
Copying over lib dir too
Adding helper functions, reworking how MDF is initialized

Commits got too entangled, so this is more than one.  Sorry
Not initializing git dir if command is `:uninstall`
Special functions no longer needed
Making shell functions quiet by default
Making sure mdf isn't called with invalid commands
Adding and stubbing out `use` command
Reworking git commands to not use environmental variables

so that they can be a bit more flexible