add st command to display current configuration of apps/services

[ccheetham]

Currently, one must peek into the steeltoe.yml file.

E.g.

% cat steeltoe.yml
apps: {}
services:
  mydb:
    type: postgresql
    deployArgs: {}

Adding a command to prettify the contents to a console would be helpful and also decouple a user from having to know st storage format.

Perhaps something like:

% st show
Name               Type
mydb               postgresql

[jkonicki]

@ccheetham Update description or close