Use Solution Templates when creating a new sandbox

[alansemenov]

• Selection of a solution template should be the first step of sandbox creation (before providing a sandbox name)
• Default behaviour is that user always have to select a template:

Select a template for the new sandbox:
* Headless 
* CMS
* ...
* Clean/empty

• Support an argument to skip selection of a template: --skip-template
• Support a parameter (-t or --template) to specify a template: -t headless or --template nextjs. Template name should match value of the _name field in the Guillotine response. If no match found, show the full list of templates to choose from.

[pmi]

Decided to save the selected template in a JSON format as an array of objects, containing app id and config.