Feature: when executing ssdev commands in subdirectories, there should be a warning when no project is present

[mleutenegger]

Currently, commands like serve, down, run use the current directory as working direcory. When a User is in a subdirectory, this might cause problems with mounting said subdirectory or not correctly removing containers.

A simple solution would be to check wether the current working directory contains a composer.json file and is not located under vendors/ (as modules are not a valid project in most cases).

A PR must fulfill the following:

• when executing up, down, serve, exec or run in a project containing a composer file, everything works correctly
• when executing up, down, serve, exec or run in a directory of a vendor module, a warning is thrown that ssdev is not intended for use in modules
• when executing up, down, serve, exec or run in any other directory, a warning is thrown that no project could be found