Overide of default distro

[gbraad]

Fixes #4

With the config file:

{
   "distro": "fedora33"
}

it is possible to override default shell.
If not set the default is assumed.
If the distro does not exists:

PS> $
There is no distribution with the supplied name.        

(This error is provided by the wsl command).

• Allow override of default distro
• Remove erroneous subdirectory in copy

[gbraad]

Didn't provide the -d option at the moment