new "exo add" command

[kevgo]

When adding features to an Exosphere application I want to be able to scaffold new services based on templates defined by the tech lead So that I can get started quickly with the correct service structure.

• running "exo add" adds a new service to the current application
• the available templates are in the ".exosphere" folder of the code base
• the command asks which template to use
• the command asks for information it needs for the chosen template
• the command is written in Go
• the command uses Boilr to execute the templates

Scenario: 
  Given I am in the root directory of an empty Exosphere application
  And my codebase contains the template folder ".exosphere/foo" with the files:
    | NAME                     | CONTENT                      |
    | project.json             | { "Name": "foo" }            |
    | template/{{Name}}/foo.md | This is the {{Name}} service |
  When running "exo add" and entering the values: 
    | PROGRAM OUTPUT                   | TEXT ENTERED |
    | which template to use            | 1            | 
    | Please choose a value for "Name" | my-service   | 
  Then it creates the file "my-service/foo.md" with the content:
    """
    This is the my-service service
    """
  And my "application.yml" file now has the content:
    """
    ...
   """

[cheahuychou]

closed in: https://github.com/Originate/exosphere/commit/894de6544402d418ef6fa9196f1251ee31f51451